--- a/devtools/client/animationinspector/components/animation-details.js
+++ b/devtools/client/animationinspector/components/animation-details.js
@@ -85,17 +85,17 @@ AnimationDetails.prototype = {
    * @param {Array} CSS property names.
    *                e.g. ["background-color", "opacity", ...]
    * @return {Object} Animation type mapped with CSS property name.
    *                  e.g. { "background-color": "color", }
    *                         "opacity": "float", ... }
    */
   async getAnimationTypes(propertyNames) {
     if (this.serverTraits.hasGetAnimationTypes) {
-      return await this.animation.getAnimationTypes(propertyNames);
+      return this.animation.getAnimationTypes(propertyNames);
     }
     // Set animation type 'none' since does not support getAnimationTypes.
     const animationTypes = {};
     propertyNames.forEach(propertyName => {
       animationTypes[propertyName] = "none";
     });
     return Promise.resolve(animationTypes);
   },

--- a/devtools/client/animationinspector/test/browser_animation_detail_displayed.js
+++ b/devtools/client/animationinspector/test/browser_animation_detail_displayed.js
@@ -76,10 +76,10 @@ add_task(async function() {
  * @param {AnimationTimeline} AnimationTimeline component
  * @param {DOMNode} animation-detail element
  * @return {Promise} which wait for close the detail pane
  */
 async function clickCloseButtonForDetailPanel(timeline, element) {
   const button = element.querySelector(".animation-detail-header button");
   const onclosed = timeline.once("animation-detail-closed");
   EventUtils.sendMouseEvent({type: "click"}, button, element.ownerDocument.defaultView);
-  return await onclosed;
+  return onclosed;
 }

--- a/devtools/client/animationinspector/test/head.js
+++ b/devtools/client/animationinspector/test/head.js
@@ -82,30 +82,30 @@ async function reloadTab(inspector) {
  * loaded in the toolbox
  * @param {String} reason
  *        Defaults to "test" which instructs the inspector not
  *        to highlight the node upon selection
  * @return {Promise} Resolves when the inspector is updated with the new node
            and animations of its subtree are properly displayed.
  */
 var selectNodeAndWaitForAnimations = async function(data, inspector, reason = "test") {
-    // We want to make sure the rest of the test waits for the animations to
-    // be properly displayed (wait for all target DOM nodes to be previewed).
-    let {AnimationsController, AnimationsPanel} =
-      inspector.sidebar.getWindowForTab(TAB_NAME);
-    let onUiUpdated = AnimationsPanel.once(AnimationsPanel.UI_UPDATED_EVENT);
+  // We want to make sure the rest of the test waits for the animations to
+  // be properly displayed (wait for all target DOM nodes to be previewed).
+  let {AnimationsController, AnimationsPanel} =
+    inspector.sidebar.getWindowForTab(TAB_NAME);
+  let onUiUpdated = AnimationsPanel.once(AnimationsPanel.UI_UPDATED_EVENT);
 
-    await selectNode(data, inspector, reason);
+  await selectNode(data, inspector, reason);
 
-    await onUiUpdated;
-    if (AnimationsController.animationPlayers.length !== 0) {
-      await waitForAnimationTimelineRendering(AnimationsPanel);
-      await waitForAllAnimationTargets(AnimationsPanel);
-    }
-  };
+  await onUiUpdated;
+  if (AnimationsController.animationPlayers.length !== 0) {
+    await waitForAnimationTimelineRendering(AnimationsPanel);
+    await waitForAllAnimationTargets(AnimationsPanel);
+  }
+};
 
 /**
  * Check if there are the expected number of animations being displayed in the
  * panel right now.
  * @param {AnimationsPanel} panel
  * @param {Number} nbAnimations The expected number of animations.
  * @param {String} msg An optional string to be used as the assertion message.
  */
@@ -395,17 +395,17 @@ async function clickOnTimelineHeader(pan
 
   const header = timeline.timeHeaderEl;
   const clientX = header.offsetLeft + header.offsetWidth * position;
   EventUtils.sendMouseEvent({ type: "mousedown", clientX: clientX },
                             header, header.ownerDocument.defaultView);
   info(`Click at (${ clientX }, 0) on timeline header`);
   EventUtils.sendMouseEvent({ type: "mouseup", clientX: clientX }, header,
                             header.ownerDocument.defaultView);
-  return await onTimelineDataChanged;
+  return onTimelineDataChanged;
 }
 
 /**
  * Prevent the toolbox common highlighter from making backend requests.
  * @param {Toolbox} toolbox
  */
 function disableHighlighter(toolbox) {
   toolbox._highlighter = {
@@ -442,17 +442,17 @@ async function clickOnAnimation(panel, i
   let x = timeBlockBounds.width / 2;
   let y = timeBlockBounds.height / 2;
   if (timeBlock != timeBlock.ownerDocument.elementFromPoint(x, y)) {
     // Move the mouse pointer a little since scrubber element may be at the point.
     x += timeBlockBounds.width / 4;
   }
   EventUtils.synthesizeMouse(timeBlock, x, y, {}, timeBlock.ownerDocument.defaultView);
 
-  return await onSelectionChanged;
+  return onSelectionChanged;
 }
 
 /**
  * Get an instance of the Keyframes component from the timeline.
  * @param {AnimationsPanel} panel The panel instance.
  * @param {String} propertyName The name of the animated property.
  * @return {Keyframes} The Keyframes component instance.
  */