--- a/devtools/client/animationinspector/animation-controller.js
+++ b/devtools/client/animationinspector/animation-controller.js
@@ -59,20 +59,20 @@ var shutdown = Task.async(function* () {
   if (typeof AnimationsPanel !== "undefined") {
     yield AnimationsPanel.destroy();
   }
   gToolbox = gInspector = null;
 });
 
 // This is what makes the sidebar widget able to load/unload the panel.
 function setPanel(panel) {
-  return startup(panel).catch(e => console.error(e));
+  return startup(panel).catch(console.error);
 }
 function destroy() {
-  return shutdown().catch(e => console.error(e));
+  return shutdown().catch(console.error);
 }
 
 /**
  * Get all the server-side capabilities (traits) so the UI knows whether or not
  * features should be enabled/disabled.
  * @param {Target} target The current toolbox target.
  * @return {Object} An object with boolean properties.
  */
@@ -256,17 +256,17 @@ var AnimationsController = {
    */
   toggleAll: function () {
     if (!this.traits.hasToggleAll) {
       return promise.resolve();
     }
 
     return this.animationsFront.toggleAll()
       .then(() => this.emit(this.ALL_ANIMATIONS_TOGGLED_EVENT, this))
-      .catch(e => console.error(e));
+      .catch(console.error);
   },
 
   /**
    * Similar to toggleAll except that it only plays/pauses the currently known
    * animations (those listed in this.animationPlayers).
    * @param {Boolean} shouldPause True if the animations should be paused, false
    * if they should be played.
    * @return {Promise} Resolves when the playState has been changed.

--- a/devtools/client/animationinspector/animation-panel.js
+++ b/devtools/client/animationinspector/animation-panel.js
@@ -174,19 +174,19 @@ var AnimationsPanel = {
   },
 
   onKeyDown: function (event) {
     // If the space key is pressed, it should toggle the play state of
     // the animations displayed in the panel, or of all the animations on
     // the page if the selected node does not have any animation on it.
     if (event.keyCode === KeyCodes.DOM_VK_SPACE) {
       if (AnimationsController.animationPlayers.length > 0) {
-        this.playPauseTimeline().catch(ex => console.error(ex));
+        this.playPauseTimeline().catch(console.error);
       } else {
-        this.toggleAll().catch(ex => console.error(ex));
+        this.toggleAll().catch(console.error);
       }
       event.preventDefault();
     }
   },
 
   togglePlayers: function (isVisible) {
     if (isVisible) {
       document.body.removeAttribute("empty");
@@ -203,30 +203,30 @@ var AnimationsPanel = {
     this.pickerButtonEl.classList.add("checked");
   },
 
   onPickerStopped: function () {
     this.pickerButtonEl.classList.remove("checked");
   },
 
   onToggleAllClicked: function () {
-    this.toggleAll().catch(ex => console.error(ex));
+    this.toggleAll().catch(console.error);
   },
 
   /**
    * Toggle (pause/play) all animations in the current target
    * and update the UI the toggleAll button.
    */
   toggleAll: Task.async(function* () {
     this.toggleAllButtonEl.classList.toggle("paused");
     yield AnimationsController.toggleAll();
   }),
 
   onTimelinePlayClicked: function () {
-    this.playPauseTimeline().catch(ex => console.error(ex));
+    this.playPauseTimeline().catch(console.error);
   },
 
   /**
    * Depending on the state of the timeline either pause or play the animations
    * displayed in it.
    * If the animations are finished, this will play them from the start again.
    * If the animations are playing, this will pause them.
    * If the animations are paused, this will resume them.
@@ -236,17 +236,17 @@ var AnimationsPanel = {
    */
   playPauseTimeline: function () {
     return AnimationsController
       .toggleCurrentAnimations(this.timelineData.isMoving)
       .then(() => this.refreshAnimationsStateAndUI());
   },
 
   onTimelineRewindClicked: function () {
-    this.rewindTimeline().catch(ex => console.error(ex));
+    this.rewindTimeline().catch(console.error);
   },
 
   /**
    * Reset the startTime of all current animations shown in the timeline and
    * pause them.
    *
    * @return {Promise} Resolves when currentTime is set and the UI is refreshed
    */
@@ -258,17 +258,17 @@ var AnimationsPanel = {
 
   /**
    * Set the playback rate of all current animations shown in the timeline to
    * the value of this.rateSelectorEl.
    */
   onRateChanged: function (e, rate) {
     AnimationsController.setPlaybackRateAll(rate)
                         .then(() => this.refreshAnimationsStateAndUI())
-                        .catch(ex => console.error(ex));
+                        .catch(console.error);
   },
 
   onTabNavigated: function () {
     this.toggleAllButtonEl.classList.remove("paused");
   },
 
   onTimelineDataChanged: function (e, data) {
     this.timelineData = data;
@@ -284,17 +284,17 @@ var AnimationsPanel = {
 
     // If the timeline data changed as a result of the user dragging the
     // scrubber, then pause all animations and set their currentTimes.
     // (Note that we want server-side requests to be sequenced, so we only do
     // this after the previous currentTime setting was done).
     if (isUserDrag && !this.setCurrentTimeAllPromise) {
       this.setCurrentTimeAllPromise =
         AnimationsController.setCurrentTimeAll(time, true)
-                            .catch(error => console.error(error))
+                            .catch(console.error)
                             .then(() => {
                               this.setCurrentTimeAllPromise = null;
                             });
     }
 
     this.displayTimelineCurrentTime();
   },
 

--- a/devtools/client/canvasdebugger/callslist.js
+++ b/devtools/client/canvasdebugger/callslist.js
@@ -283,17 +283,17 @@ var CallsListView = Heritage.extend(Widg
     setConditionalTimeout("screenshot-display", SCREENSHOT_DISPLAY_DELAY, () => {
       return !this._isSliding;
     }, () => {
       let frameSnapshot = SnapshotsListView.selectedItem.attachment.actor;
       let functionCall = callItem.attachment.actor;
       frameSnapshot.generateScreenshotFor(functionCall).then(screenshot => {
         this.showScreenshot(screenshot);
         this.highlightedThumbnail = screenshot.index;
-      }).catch(e => console.error(e));
+      }).catch(console.error);
     });
   },
 
   /**
    * The mousedown listener for the call selection slider.
    */
   _onSlideMouseDown: function () {
     this._isSliding = true;

--- a/devtools/client/inspector/boxmodel/box-model.js
+++ b/devtools/client/inspector/boxmodel/box-model.js
@@ -297,37 +297,37 @@ BoxModel.prototype = {
             properties.push({ name: bprop, value: "solid" });
           }
         }
 
         if (property.substring(0, 9) == "position-") {
           properties[0].name = property.substring(9);
         }
 
-        session.setProperties(properties).catch(e => console.error(e));
+        session.setProperties(properties).catch(console.error);
       },
       done: (value, commit) => {
         editor.elt.parentNode.classList.remove("boxmodel-editing");
         if (!commit) {
           session.revert().then(() => {
             session.destroy();
-          }, e => console.error(e));
+          }, console.error);
           return;
         }
 
         if (!this.inspector) {
           return;
         }
 
         let node = this.inspector.selection.nodeFront;
         this.inspector.pageStyle.getLayout(node, {
           autoMargins: true,
         }).then(layout => {
           this.store.dispatch(updateLayout(layout));
-        }, e => console.error(e));
+        }, console.error);
       },
       cssProperties: getCssProperties(this.inspector.toolbox)
     }, event);
   },
 
   /**
    * Shows the box-model highlighter on the currently selected element.
    *

--- a/devtools/client/inspector/computed/computed.js
+++ b/devtools/client/inspector/computed/computed.js
@@ -504,17 +504,17 @@ CssComputedView.prototype = {
 
               this.inspector.emit("computed-view-refreshed");
               resolve(undefined);
             }
           }
         );
         this._refreshProcess.schedule();
       });
-    }).catch((err) => console.error(err));
+    }).catch(console.error);
   },
 
   /**
    * Handle the shortcut events in the computed view.
    */
   _onShortcut: function (name, event) {
     if (!event.target.closest("#sidebar-panel-computedview")) {
       return;

--- a/devtools/client/inspector/inspector-commands.js
+++ b/devtools/client/inspector/inspector-commands.js
@@ -53,33 +53,33 @@ exports.items = [{
     }, {
       name: "hide",
       type: "boolean",
       hidden: true
     }]
   }],
   exec: function* (args, context) {
     if (args.hide) {
-      context.updateExec("eyedropper_server_hide").catch(e => console.error(e));
+      context.updateExec("eyedropper_server_hide").catch(console.error);
       return;
     }
 
     // If the inspector is already picking a color from the page, cancel it.
     let target = context.environment.target;
     let toolbox = gDevTools.getToolbox(target);
     if (toolbox) {
       let inspector = toolbox.getPanel("inspector");
       if (inspector) {
         yield inspector.hideEyeDropper();
       }
     }
 
     let telemetry = new Telemetry();
     telemetry.toolOpened(args.frommenu ? "menueyedropper" : "eyedropper");
-    context.updateExec("eyedropper_server").catch(e => console.error(e));
+    context.updateExec("eyedropper_server").catch(console.error);
   }
 }, {
   item: "command",
   runAt: "server",
   name: "eyedropper_server",
   hidden: true,
   exec: function (args, {environment}) {
     let eyeDropper = windowEyeDroppers.get(environment.window);

--- a/devtools/client/inspector/inspector-search.js
+++ b/devtools/client/inspector/inspector-search.js
@@ -67,17 +67,17 @@ InspectorSearch.prototype = {
     this.searchClearButton.removeEventListener("click", this._onClearSearch);
     this.searchBox = null;
     this.searchClearButton = null;
     this.autocompleter.destroy();
   },
 
   _onSearch: function (reverse = false) {
     this.doFullTextSearch(this.searchBox.value, reverse)
-        .catch(e => console.error(e));
+        .catch(console.error);
   },
 
   doFullTextSearch: Task.async(function* (query, reverse) {
     let lastSearched = this._lastSearched;
     this._lastSearched = query;
 
     if (query.length === 0) {
       this.searchBox.classList.remove("devtools-style-searchbox-no-match");

--- a/devtools/client/inspector/inspector.js
+++ b/devtools/client/inspector/inspector.js
@@ -219,23 +219,23 @@ Inspector.prototype = {
     this._supportsResolveRelativeURL = false;
 
     // Use getActorDescription first so that all actorHasMethod calls use
     // a cached response from the server.
     return this._target.getActorDescription("domwalker").then(desc => {
       return promise.all([
         this._target.actorHasMethod("domwalker", "duplicateNode").then(value => {
           this._supportsDuplicateNode = value;
-        }).catch(e => console.error(e)),
+        }).catch(console.error),
         this._target.actorHasMethod("domnode", "scrollIntoView").then(value => {
           this._supportsScrollIntoView = value;
-        }).catch(e => console.error(e)),
+        }).catch(console.error),
         this._target.actorHasMethod("inspector", "resolveRelativeURL").then(value => {
           this._supportsResolveRelativeURL = value;
-        }).catch(e => console.error(e)),
+        }).catch(console.error),
       ]);
     });
   },
 
   _deferredOpen: function (defaultSelection) {
     this.breadcrumbs = new HTMLBreadcrumbs(this);
 
     this.walker.on("new-root", this.onNewRoot);
@@ -1622,34 +1622,34 @@ Inspector.prototype = {
     if (!this.eyeDropperButton) {
       return null;
     }
 
     this.telemetry.toolOpened("toolbareyedropper");
     this.eyeDropperButton.classList.add("checked");
     this.startEyeDropperListeners();
     return this.inspector.pickColorFromPage(this.toolbox, {copyOnSelect: true})
-                         .catch(e => console.error(e));
+                         .catch(console.error);
   },
 
   /**
    * Hide the eyedropper.
    * @return {Promise} resolves when the eyedropper is hidden.
    */
   hideEyeDropper: function () {
     // The eyedropper button doesn't exist, most probably because the actor doesn't
     // support the pickColorFromPage, or because the page isn't HTML.
     if (!this.eyeDropperButton) {
       return null;
     }
 
     this.eyeDropperButton.classList.remove("checked");
     this.stopEyeDropperListeners();
     return this.inspector.cancelPickColorFromPage()
-                         .catch(e => console.error(e));
+                         .catch(console.error);
   },
 
   /**
    * Create a new node as the last child of the current selection, expand the
    * parent and select the new node.
    */
   addNode: Task.async(function* () {
     if (!this.canAddHTMLChild()) {
@@ -1834,74 +1834,74 @@ Inspector.prototype = {
    * @param  {Promise} longStringActorPromise
    *         promise expected to resolve a LongStringActor instance
    * @return {Promise} promise resolving (with no argument) when the
    *         string is sent to the clipboard
    */
   _copyLongString: function (longStringActorPromise) {
     return this._getLongString(longStringActorPromise).then(string => {
       clipboardHelper.copyString(string);
-    }).catch(e => console.error(e));
+    }).catch(console.error);
   },
 
   /**
    * Retrieve the content of a longString (via a promise resolving a LongStringActor)
    * @param  {Promise} longStringActorPromise
    *         promise expected to resolve a LongStringActor instance
    * @return {Promise} promise resolving with the retrieved string as argument
    */
   _getLongString: function (longStringActorPromise) {
     return longStringActorPromise.then(longStringActor => {
       return longStringActor.string().then(string => {
-        longStringActor.release().catch(e => console.error(e));
+        longStringActor.release().catch(console.error);
         return string;
       });
-    }).catch(e => console.error(e));
+    }).catch(console.error);
   },
 
   /**
    * Copy a unique selector of the selected Node to the clipboard.
    */
   copyUniqueSelector: function () {
     if (!this.selection.isNode()) {
       return;
     }
 
     this.telemetry.toolOpened("copyuniquecssselector");
     this.selection.nodeFront.getUniqueSelector().then(selector => {
       clipboardHelper.copyString(selector);
-    }).catch(e => console.error);
+    }).catch(console.error);
   },
 
   /**
    * Copy the full CSS Path of the selected Node to the clipboard.
    */
   copyCssPath: function () {
     if (!this.selection.isNode()) {
       return;
     }
 
     this.telemetry.toolOpened("copyfullcssselector");
     this.selection.nodeFront.getCssPath().then(path => {
       clipboardHelper.copyString(path);
-    }).catch(e => console.error);
+    }).catch(console.error);
   },
 
   /**
    * Copy the XPath of the selected Node to the clipboard.
    */
   copyXPath: function () {
     if (!this.selection.isNode()) {
       return;
     }
 
     this.telemetry.toolOpened("copyxpath");
     this.selection.nodeFront.getXPath().then(path => {
       clipboardHelper.copyString(path);
-    }).catch(e => console.error);
+    }).catch(console.error);
   },
 
   /**
    * Initiate gcli screenshot command on selected node.
    */
   screenshotNode: Task.async(function* () {
     const command = Services.prefs.getBoolPref("devtools.screenshot.clipboard.enabled") ?
       "screenshot --file --clipboard --selector" :
@@ -1937,17 +1937,17 @@ Inspector.prototype = {
   duplicateNode: function () {
     let selection = this.selection;
     if (!selection.isElementNode() ||
         selection.isRoot() ||
         selection.isAnonymousNode() ||
         selection.isPseudoElementNode()) {
       return;
     }
-    this.walker.duplicateNode(selection.nodeFront).catch(e => console.error(e));
+    this.walker.duplicateNode(selection.nodeFront).catch(console.error);
   },
 
   /**
    * Delete the selected node.
    */
   deleteNode: function () {
     if (!this.selection.isNode() ||
          this.selection.isRoot()) {
@@ -2038,28 +2038,28 @@ Inspector.prototype = {
             let browserWin = this.target.tab.ownerDocument.defaultView;
             browserWin.openUILinkIn(url, "tab");
           } else if (type === "cssresource") {
             return this.toolbox.viewSourceInStyleEditor(url);
           } else if (type === "jsresource") {
             return this.toolbox.viewSourceInDebugger(url);
           }
           return null;
-        }).catch(e => console.error(e));
+        }).catch(console.error);
     } else if (type == "idref") {
       // Select the node in the same document.
       this.walker.document(this.selection.nodeFront).then(doc => {
         return this.walker.querySelector(doc, "#" + CSS.escape(link)).then(node => {
           if (!node) {
             this.emit("idref-attribute-link-failed");
             return;
           }
           this.selection.setNodeFront(node);
         });
-      }).catch(e => console.error(e));
+      }).catch(console.error);
     }
   },
 
   /**
    * This method is here for the benefit of the node-menu-link-copy menu item
    * in the inspector contextual-menu.
    */
   onCopyLink: function () {

--- a/devtools/client/inspector/markup/markup.js
+++ b/devtools/client/inspector/markup/markup.js
@@ -179,17 +179,17 @@ MarkupView.prototype = {
 
   _disableImagePreviewTooltip: function () {
     this.imagePreviewTooltip.stopTogglingOnHover();
   },
 
   _onToolboxPickerHover: function (event, nodeFront) {
     this.showNode(nodeFront).then(() => {
       this._showContainerAsHovered(nodeFront);
-    }, e => console.error(e));
+    }, console.error);
   },
 
   /**
    * If the element picker gets canceled, make sure and re-center the view on the
    * current selected element.
    */
   _onToolboxPickerCanceled: function () {
     if (this._selectedContainer) {

--- a/devtools/client/inspector/rules/rules.js
+++ b/devtools/client/inspector/rules/rules.js
@@ -892,17 +892,17 @@ CssRuleView.prototype = {
 
       this._clearRules();
       let onEditorsReady = this._createEditors();
       this.refreshPseudoClassPanel();
 
       // Notify anyone that cares that we refreshed.
       return onEditorsReady.then(() => {
         this.emit("ruleview-refreshed");
-      }, e => console.error(e));
+      }, console.error);
     }).catch(promiseWarn);
   },
 
   /**
    * Show the user that the rule view has no node selected.
    */
   _showEmpty: function () {
     if (this.styleDocument.getElementById("ruleview-no-results")) {

--- a/devtools/client/inspector/rules/views/rule-editor.js
+++ b/devtools/client/inspector/rules/views/rule-editor.js
@@ -270,17 +270,17 @@ RuleEditor.prototype = {
     let showOrig = Services.prefs.getBoolPref(PREF_ORIG_SOURCES);
     if (showOrig && !this.rule.isSystem &&
         this.rule.domRule.type !== ELEMENT_STYLE) {
       // Only get the original source link if the right pref is set, if the rule
       // isn't a system rule and if it isn't an inline rule.
       this.rule.getOriginalSourceStrings().then((strings) => {
         sourceLabel.textContent = strings.short;
         sourceLabel.setAttribute("title", strings.full);
-      }, e => console.error(e)).then(() => {
+      }, console.error).then(() => {
         this.emit("source-link-updated");
       });
     } else {
       // If we're not getting the original source link, then we can emit the
       // event immediately (but still asynchronously to give consumers a chance
       // to register it after having instantiated the RuleEditor).
       promise.resolve().then(() => {
         this.emit("source-link-updated");

--- a/devtools/client/inspector/shared/dom-node-preview.js
+++ b/devtools/client/inspector/shared/dom-node-preview.js
@@ -191,17 +191,17 @@ DomNodePreview.prototype = {
     this.inspector.off("markupmutation", this.onMarkupMutations);
     this.previewEl.removeEventListener("mouseover", this.onPreviewMouseOver);
     this.previewEl.removeEventListener("mouseout", this.onPreviewMouseOut);
     this.previewEl.removeEventListener("click", this.onSelectElClick);
     this.highlightNodeEl.removeEventListener("click", this.onHighlightElClick);
   },
 
   destroy: function () {
-    HighlighterLock.unhighlight().catch(e => console.error(e));
+    HighlighterLock.unhighlight().catch(console.error);
 
     this.stopListeners();
 
     this.el.remove();
     this.el = this.tagNameEl = this.idEl = this.classEl = this.pseudoEl = null;
     this.highlightNodeEl = this.previewEl = null;
     this.nodeFront = this.inspector = null;
   },
@@ -213,25 +213,25 @@ DomNodePreview.prototype = {
     return null;
   },
 
   onPreviewMouseOver: function () {
     if (!this.nodeFront || !this.highlighterUtils) {
       return;
     }
     this.highlighterUtils.highlightNodeFront(this.nodeFront)
-                         .catch(e => console.error(e));
+                         .catch(console.error);
   },
 
   onPreviewMouseOut: function () {
     if (!this.nodeFront || !this.highlighterUtils) {
       return;
     }
     this.highlighterUtils.unhighlight()
-                         .catch(e => console.error(e));
+                         .catch(console.error);
   },
 
   onSelectElClick: function () {
     if (!this.nodeFront) {
       return;
     }
     this.inspector.selection.setNodeFront(this.nodeFront, "dom-node-preview");
   },
@@ -241,22 +241,22 @@ DomNodePreview.prototype = {
 
     let classList = this.highlightNodeEl.classList;
     let isHighlighted = classList.contains("selected");
 
     if (isHighlighted) {
       classList.remove("selected");
       HighlighterLock.unhighlight().then(() => {
         this.emit("target-highlighter-unlocked");
-      }, error => console.error(error));
+      }, console.error);
     } else {
       classList.add("selected");
       HighlighterLock.highlight(this).then(() => {
         this.emit("target-highlighter-locked");
-      }, error => console.error(error));
+      }, console.error);
     }
   },
 
   onHighlighterLocked: function (e, domNodePreview) {
     if (domNodePreview !== this) {
       this.highlightNodeEl.classList.remove("selected");
     }
   },

--- a/devtools/client/inspector/shared/highlighters-overlay.js
+++ b/devtools/client/inspector/shared/highlighters-overlay.js
@@ -530,17 +530,17 @@ HighlightersOverlay.prototype = {
     }
 
     // For some reason, the call to highlighter.hide doesn't always return a
     // promise. This causes some tests to fail when trying to install a
     // rejection handler on the result of the call. To avoid this, check
     // whether the result is truthy before installing the handler.
     let onHidden = this.highlighters[this.hoveredHighlighterShown].hide();
     if (onHidden) {
-      onHidden.catch(e => console.error(e));
+      onHidden.catch(console.error);
     }
 
     this.hoveredHighlighterShown = null;
     this.emit("highlighter-hidden");
   },
 
   /**
    * Is the current hovered node a css transform property value in the

--- a/devtools/client/responsive.html/manager.js
+++ b/devtools/client/responsive.html/manager.js
@@ -184,17 +184,17 @@ const ResponsiveUIManager = exports.Resp
       case "resize off":
         completed = this.closeIfNeeded(window, tab, { command: true });
         break;
       case "resize toggle":
         completed = this.toggle(window, tab, { command: true });
         break;
       default:
     }
-    completed.catch(e => console.error(e));
+    completed.catch(console.error);
   },
 
   handleMenuCheck({target}) {
     ResponsiveUIManager.setMenuCheckFor(target);
   },
 
   initMenuCheckListenerFor(window) {
     let { tabContainer } = window.gBrowser;

--- a/devtools/client/scratchpad/scratchpad.js
+++ b/devtools/client/scratchpad/scratchpad.js
@@ -1731,17 +1731,17 @@ var Scratchpad = {
       if (state)
         this.dirty = !state.saved;
 
       this.initialized = true;
       this._triggerObservers("Ready");
       this.populateRecentFilesMenu();
       PreferenceObserver.init();
       CloseObserver.init();
-    }).catch((err) => console.error(err));
+    }).catch(console.error);
     this._setupCommandListeners();
     this._updateViewMenuItems();
     this._setupPopupShowingListeners();
 
     // Change the accesskey for the help menu as it can be specific on Windows
     // some localizations of Windows (ex:french, german) use "?"
     //  for the help button in the menubar but Gnome does not.
     if (Services.appinfo.OS == "WINNT") {

--- a/devtools/client/shadereditor/shadereditor.js
+++ b/devtools/client/shadereditor/shadereditor.js
@@ -309,17 +309,17 @@ var ShadersListView = Heritage.extend(Wi
         vs: vertexShaderText,
         fs: fragmentShaderText
       });
     }
 
     getShaders()
       .then(getSources)
       .then(showSources)
-      .catch(e => console.error(e));
+      .catch(console.error);
   },
 
   /**
    * The check listener for the programs container.
    */
   _onProgramCheck: function ({ detail: { checked }, target }) {
     let sourceItem = this.getItemForElement(target);
     let attachment = sourceItem.attachment;

--- a/devtools/client/shared/widgets/FilterWidget.js
+++ b/devtools/client/shared/widgets/FilterWidget.js
@@ -570,25 +570,25 @@ CSSFilterEditorWidget.prototype = {
 
     let id = +preset.dataset.id;
 
     this.getPresets().then(presets => {
       if (el.classList.contains("remove-button")) {
         // If the click happened on the remove button.
         presets.splice(id, 1);
         this.setPresets(presets).then(this.renderPresets,
-                                      ex => console.error(ex));
+                                      console.error);
       } else {
         // Or if the click happened on a preset.
         let p = presets[id];
 
         this.setCssValue(p.value);
         this.addPresetInput.value = p.name;
       }
-    }, ex => console.error(ex));
+    }, console.error);
   },
 
   _togglePresets: function () {
     this.el.classList.toggle("show-presets");
     this.emit("render");
   },
 
   _savePreset: function (e) {
@@ -607,18 +607,18 @@ CSSFilterEditorWidget.prototype = {
 
       if (index > -1) {
         presets[index].value = value;
       } else {
         presets.push({name, value});
       }
 
       this.setPresets(presets).then(this.renderPresets,
-                                    ex => console.error(ex));
-    }, ex => console.error(ex));
+                                    console.error);
+    }, console.error);
   },
 
   /**
    * Workaround needed to reset the focus when using a HTML select inside a XUL panel.
    * See Bug 1294366.
    */
   _resetFocus: function () {
     this.filterSelect.ownerDocument.defaultView.focus();
@@ -947,22 +947,22 @@ CSSFilterEditorWidget.prototype = {
 
   getPresets: function () {
     return asyncStorage.getItem("cssFilterPresets").then(presets => {
       if (!presets) {
         return [];
       }
 
       return presets;
-    }, e => console.error(e));
+    }, console.error);
   },
 
   setPresets: function (presets) {
     return asyncStorage.setItem("cssFilterPresets", presets)
-      .catch(e => console.error(e));
+      .catch(console.error);
   }
 };
 
 // Fixes JavaScript's float precision
 function fixFloat(a, number) {
   let fixed = parseFloat(a).toFixed(1);
   return number ? parseFloat(fixed) : fixed;
 }

--- a/devtools/client/shared/widgets/tooltip/SwatchColorPickerTooltip.js
+++ b/devtools/client/shared/widgets/tooltip/SwatchColorPickerTooltip.js
@@ -166,17 +166,17 @@ SwatchColorPickerTooltip.prototype = ext
     telemetry.toolOpened("pickereyedropper");
     inspector.pickColorFromPage(toolbox, {copyOnSelect: false}).then(() => {
       this.eyedropperOpen = true;
 
       // close the colorpicker tooltip so that only the eyedropper is open.
       this.hide();
 
       this.tooltip.emit("eyedropper-opened");
-    }, e => console.error(e));
+    }, console.error);
 
     inspector.once("color-picked", color => {
       toolbox.win.focus();
       this._selectColor(color);
       this._onEyeDropperDone();
     });
 
     inspector.once("color-pick-canceled", () => {

--- a/devtools/client/sourceeditor/autocomplete.js
+++ b/devtools/client/sourceeditor/autocomplete.js
@@ -232,17 +232,17 @@ function autoComplete({ ed, cm }) {
     popup.setItems(suggestions);
 
     popup.once("popup-opened", () => {
       // This event is used in tests.
       ed.emit("after-suggest");
     });
     popup.openPopup(cursorElement, -1 * left, 0);
     autocompleteOpts.suggestionInsertedOnce = false;
-  }).catch(e => console.error(e));
+  }).catch(console.error);
 }
 
 /**
  * Inserts a popup item into the current cursor location
  * in the editor.
  */
 function insertPopupItem(ed, popupItem) {
   let {preLabel, text} = popupItem;

--- a/devtools/client/styleeditor/StyleEditorUI.jsm
+++ b/devtools/client/styleeditor/StyleEditorUI.jsm
@@ -229,17 +229,17 @@ StyleEditorUI.prototype = {
    * @param {string} event
    *        Event name
    * @param {StyleSheet} styleSheet
    *        StyleSheet object for new sheet
    */
   _onNewDocument: function () {
     this._debuggee.getStyleSheets().then((styleSheets) => {
       return this._resetStyleSheetList(styleSheets);
-    }).catch(e => console.error(e));
+    }).catch(console.error);
   },
 
   /**
    * Add editors for all the given stylesheets to the UI.
    *
    * @param  {array} styleSheets
    *         Array of StyleSheetFront
    */
@@ -629,17 +629,17 @@ StyleEditorUI.prototype = {
             let lineCount = editorText.split("\n").length;
             let ruleCount = showEditor.styleSheet.ruleCount;
             if (lineCount >= ruleCount) {
               showEditor.addUnusedRegions(reports);
             } else {
               this.emit("error", { key: "error-compressed", level: "info" });
             }
           }
-        }.bind(this)).catch(e => console.error(e));
+        }.bind(this)).catch(console.error);
       }
     });
   },
 
   /**
    * Switch to the editor that has been marked to be selected.
    *
    * @return {Promise}
@@ -914,17 +914,17 @@ StyleEditorUI.prototype = {
         div.appendChild(link);
 
         list.appendChild(div);
       }
 
       sidebar.hidden = !showSidebar || !inSource;
 
       this.emit("media-list-changed", editor);
-    }.bind(this)).catch(e => console.error(e));
+    }.bind(this)).catch(console.error);
   },
 
   /**
    * Used to safely inject media query links
    *
    * @param {HTMLElement} element
    *        The element corresponding to the media sidebar condition
    * @param {String} rawText

--- a/devtools/client/styleeditor/StyleSheetEditor.jsm
+++ b/devtools/client/styleeditor/StyleSheetEditor.jsm
@@ -122,17 +122,17 @@ function StyleSheetEditor(styleSheet, wi
   this._onMouseMove = this._onMouseMove.bind(this);
 
   this._focusOnSourceEditorReady = false;
   this.cssSheet.on("property-change", this._onPropertyChange);
   this.styleSheet.on("error", this._onError);
   this.mediaRules = [];
   if (this.cssSheet.getMediaRules) {
     this.cssSheet.getMediaRules().then(this._onMediaRulesChanged,
-                                       e => console.error(e));
+                                       console.error);
   }
   this.cssSheet.on("media-rules-changed", this._onMediaRulesChanged);
   this.cssSheet.on("style-applied", this._onStyleApplied);
   this.savedFile = file;
   this.linkCSSFile();
 }
 this.StyleSheetEditor = StyleSheetEditor;
 
@@ -513,17 +513,17 @@ StyleSheetEditor.prototype = {
     }
     this.focus();
   },
 
   /**
    * Toggled the disabled state of the underlying stylesheet.
    */
   toggleDisabled: function () {
-    this.styleSheet.toggleDisabled().catch(e => console.error(e));
+    this.styleSheet.toggleDisabled().catch(console.error);
   },
 
   /**
    * Queue a throttled task to update the live style sheet.
    */
   updateStyleSheet: function () {
     if (this._updateTask) {
       // cancel previous queued task not executed within throttle delay
@@ -555,17 +555,17 @@ StyleSheetEditor.prototype = {
     this._updateTask = null;
 
     if (this.sourceEditor) {
       this._state.text = this.sourceEditor.getText();
     }
 
     this._isUpdating = true;
     this.styleSheet.update(this._state.text, this.transitionsEnabled)
-      .catch(e => console.error(e));
+      .catch(console.error);
   },
 
   /**
    * Handle mousemove events, calling _highlightSelectorAt after a delay only
    * and reseting the delay everytime.
    */
   _onMouseMove: function (e) {
     this.highlighter.hide();

--- a/devtools/client/webconsole/console-output.js
+++ b/devtools/client/webconsole/console-output.js
@@ -3067,17 +3067,17 @@ Widgets.ObjectRenderers.add({
     }
 
     this._text(">");
 
     // Register this widget in the owner message so that it gets destroyed when
     // the message is destroyed.
     this.message.widgets.add(this);
 
-    this.linkToInspector().catch(e => console.error(e));
+    this.linkToInspector().catch(console.error);
   },
 
   /**
    * If the DOMNode being rendered can be highlit in the page, this function
    * will attach mouseover/out event listeners to do so, and the inspector icon
    * to open the node in the inspector.
    * @return a promise that resolves when the node has been linked to the
    * inspector, or rejects if it wasn't (either if no toolbox could be found to
@@ -3155,17 +3155,17 @@ Widgets.ObjectRenderers.add({
   /**
    * Unhighlight a previously highlit node
    * @see highlightDomNode
    * @return a promise that resolves when the highlighter has been hidden
    */
   unhighlightDomNode: function () {
     return this.linkToInspector().then(() => {
       return this.toolbox.highlighterUtils.unhighlight();
-    }).catch(e => console.error(e));
+    }).catch(console.error);
   },
 
   /**
    * Open the DOMNode corresponding to the ObjectActor in the inspector panel
    * @return a promise that resolves when the inspector has been switched to
    * and the node has been selected, or rejects if the node cannot be selected
    * (detached from the DOM). Note that in any case, the inspector panel will
    * be switched to.

--- a/devtools/client/webconsole/test/browser_webconsole_block_mixedcontent_securityerrors.js
+++ b/devtools/client/webconsole/test/browser_webconsole_block_mixedcontent_securityerrors.js
@@ -92,17 +92,17 @@ function mixedContentOverrideTest2(hud, 
         text: "Loading mixed (insecure) display content" +
           " \u201chttp://example.com/tests/image/test/mochitest/blue.png\u201d" +
           " on a secure page",
         category: CATEGORY_SECURITY,
         severity: SEVERITY_WARNING,
         objects: true,
       },
     ],
-  }).then(msgs => deferred.resolve(msgs), e => console.error(e));
+  }).then(msgs => deferred.resolve(msgs), console.error);
 
   return deferred.promise;
 }
 
 function testClickOpenNewTab(hud, match) {
   let warningNode = match.clickableElements[0];
   ok(warningNode, "link element");
   ok(warningNode.classList.contains("learn-more-link"), "link class name");

--- a/devtools/client/webide/content/runtimedetails.js
+++ b/devtools/client/webide/content/runtimedetails.js
@@ -97,17 +97,17 @@ function CheckLockState() {
         device.isRoot().then(isRoot => {
           if (isRoot) {
             adbCheckResult.textContent = sYes;
             flipCertPerfButton.removeAttribute("disabled");
           } else {
             adbCheckResult.textContent = sNo;
             adbRootAction.removeAttribute("hidden");
           }
-        }, e => console.error(e));
+        }, console.error);
       } else {
         adbCheckResult.textContent = sUnknown;
       }
     } else {
       adbCheckResult.textContent = sNotUSB;
     }
 
     // forbid-certified-apps check
@@ -115,17 +115,17 @@ function CheckLockState() {
       let prefFront = AppManager.preferenceFront;
       prefFront.getBoolPref("devtools.debugger.forbid-certified-apps").then(isForbidden => {
         if (isForbidden) {
           devtoolsCheckResult.textContent = sNo;
           flipCertPerfAction.removeAttribute("hidden");
         } else {
           devtoolsCheckResult.textContent = sYes;
         }
-      }, e => console.error(e));
+      }, console.error);
     } catch (e) {
       // Exception. pref actor is only accessible if forbird-certified-apps is false
       devtoolsCheckResult.textContent = sNo;
       flipCertPerfAction.removeAttribute("hidden");
     }
 
   }
 
@@ -142,10 +142,10 @@ function EnableCertApps() {
     "echo 'user_pref(\"network.disable.ipc.security\", true);' >> prefs.js && " +
     "echo 'user_pref(\"dom.webcomponents.enabled\", true);' >> prefs.js && " +
     "start b2g"
   );
 }
 
 function RootADB() {
   let device = AppManager.selectedRuntime.device;
-  device.summonRoot().then(CheckLockState, (e) => console.error(e));
+  device.summonRoot().then(CheckLockState, console.error);
 }

--- a/devtools/docs/backend/backward-compatibility.md
+++ b/devtools/docs/backend/backward-compatibility.md
@@ -38,17 +38,17 @@ let hasProfilerActor = toolbox.target.ha
 
 The `hasActor` method returns a boolean synchronously.
 
 2. Detecting if an actor has a given method: same thing here, you need access to the toolbox:
 
 ```js
 toolbox.target.actorHasMethod("domwalker", "duplicateNode").then(hasMethod => {
 
-}).catch(e => console.error(e));
+}).catch(console.error);
 ```
 
 The `actorHasMethod` returns a promise that resolves to a boolean.
 
 ## Removing old backward compatibility code
 
 We used to support old Firefox OS servers (back to Gecko 28), we don't anymore. Does this mean we can remove compatibility traits for it?
 

--- a/devtools/server/actors/highlighters/eye-dropper.js
+++ b/devtools/server/actors/highlighters/eye-dropper.js
@@ -378,17 +378,17 @@ EyeDropper.prototype = {
    */
   selectColor() {
     let onColorSelected = Promise.resolve();
     if (this.options.copyOnSelect) {
       onColorSelected = this.copyColor();
     }
 
     this.emit("selected", toColorString(this.centerColor, this.format));
-    onColorSelected.then(() => this.hide(), e => console.error(e));
+    onColorSelected.then(() => this.hide(), console.error);
   },
 
   /**
    * Handler for the keydown event. Either select the color or move the panel in a
    * direction depending on the key pressed.
    */
   handleKeyDown(e) {
     // Bail out early if any unsupported modifier is used, so that we let

--- a/devtools/shared/protocol.js
+++ b/devtools/shared/protocol.js
@@ -1246,17 +1246,17 @@ Front.prototype = extend(Pool.prototype,
    */
   send: function (packet) {
     if (packet.to) {
       this.conn._transport.send(packet);
     } else {
       this.actor().then(actorID => {
         packet.to = actorID;
         this.conn._transport.send(packet);
-      }).catch(e => console.error(e));
+      }).catch(console.error);
     }
   },
 
   /**
    * Send a two-way request on the connection.
    */
   request: function (packet) {
     let deferred = defer();