--- a/devtools/client/shared/test/browser_key_shortcuts.js
+++ b/devtools/client/shared/test/browser_key_shortcuts.js
@@ -1,11 +1,13 @@
 /* Any copyright is dedicated to the Public Domain.
    http://creativecommons.org/publicdomain/zero/1.0/ */
 
+"use strict";
+
 var isOSX = Services.appinfo.OS === "Darwin";
 
 add_task(function* () {
   let shortcuts = new KeyShortcuts({
     window
   });
 
   yield testSimple(shortcuts);
@@ -39,68 +41,68 @@ function once(shortcuts, key, listener) 
       called = true;
       listener(key2, event);
       done();
     };
     shortcuts.on(key, onShortcut);
   });
 }
 
-function testSimple(shortcuts) {
+function* testSimple(shortcuts) {
   info("Test simple key shortcuts");
 
   let onKey = once(shortcuts, "0", (key, event) => {
     is(event.key, "0");
 
     // Display another key press to ensure that once() correctly stop listening
     EventUtils.synthesizeKey("0", {}, window);
   });
 
   EventUtils.synthesizeKey("0", {}, window);
   yield onKey;
 }
 
-function testNonLetterCharacter(shortcuts) {
+function* testNonLetterCharacter(shortcuts) {
   info("Test non-naive character key shortcuts");
 
   let onKey = once(shortcuts, "[", (key, event) => {
     is(event.key, "[");
   });
 
   EventUtils.synthesizeKey("[", {}, window);
   yield onKey;
 }
 
-function testFunctionKey(shortcuts) {
+function* testFunctionKey(shortcuts) {
   info("Test function key shortcuts");
 
   let onKey = once(shortcuts, "F12", (key, event) => {
     is(event.key, "F12");
   });
 
   EventUtils.synthesizeKey("F12", { keyCode: 123 }, window);
   yield onKey;
 }
 
 // Plus is special. It's keycode is the one for "=". That's because it requires
 // shift to be pressed and is behind "=" key. So it should be considered as a
 // character key
-function testPlusCharacter(shortcuts) {
+function* testPlusCharacter(shortcuts) {
   info("Test 'Plus' key shortcuts");
 
   let onKey = once(shortcuts, "Plus", (key, event) => {
     is(event.key, "+");
   });
 
   EventUtils.synthesizeKey("+", { keyCode: 61, shiftKey: true }, window);
   yield onKey;
 }
 
 // Test they listeners are not mixed up between shortcuts
-function testMixup(shortcuts) {
+function* testMixup(shortcuts) {
   info("Test possible listener mixup");
 
   let hitFirst = false, hitSecond = false;
   let onFirstKey = once(shortcuts, "0", (key, event) => {
     is(event.key, "0");
     hitFirst = true;
   });
   let onSecondKey = once(shortcuts, "Alt+A", (key, event) => {
@@ -125,17 +127,17 @@ function testMixup(shortcuts) {
   // Finally dispatch the second shortcut
   EventUtils.synthesizeKey("a", { altKey: true }, window);
   yield onSecondKey;
   ok(hitSecond, "Got the second shortcut notified once it is actually fired");
 }
 
 // On azerty keyboard, digits are only available by pressing Shift/Capslock,
 // but we accept them even if we omit doing that.
-function testLooseDigits(shortcuts) {
+function* testLooseDigits(shortcuts) {
   info("Test Loose digits");
   let onKey = once(shortcuts, "0", (key, event) => {
     is(event.key, "à");
     ok(!event.altKey);
     ok(!event.ctrlKey);
     ok(!event.metaKey);
     ok(!event.shiftKey);
   });
@@ -158,17 +160,17 @@ function testLooseDigits(shortcuts) {
   EventUtils.synthesizeKey(
     "0",
     { keyCode: 48, shiftKey: true },
     window);
   yield onKey;
 }
 
 // Test that shortcuts is notified only when the modifiers match exactly
-function testExactModifiers(shortcuts) {
+function* testExactModifiers(shortcuts) {
   info("Test exact modifiers match");
 
   let hit = false;
   let onKey = once(shortcuts, "Alt+A", (key, event) => {
     is(event.key, "a");
     ok(event.altKey);
     ok(!event.ctrlKey);
     ok(!event.metaKey);
@@ -206,17 +208,17 @@ function testExactModifiers(shortcuts) {
   yield onKey;
   ok(hit, "Got shortcut notified once it is actually fired");
 }
 
 // Some keys are only accessible via shift and listener should also be called
 // even if the key didn't explicitely requested Shift modifier.
 // For example, `%` on french keyboards is only accessible via Shift.
 // Same thing for `@` on US keybords.
-function testLooseShiftModifier(shortcuts) {
+function* testLooseShiftModifier(shortcuts) {
   info("Test Loose shift modifier");
   let onKey = once(shortcuts, "%", (key, event) => {
     is(event.key, "%");
     ok(!event.altKey);
     ok(!event.ctrlKey);
     ok(!event.metaKey);
     ok(event.shiftKey);
   });
@@ -236,17 +238,17 @@ function testLooseShiftModifier(shortcut
   EventUtils.synthesizeKey(
     "@",
     { accelKey: false, altKey: false, ctrlKey: false, shiftKey: true},
     window);
   yield onKey;
 }
 
 // But Shift modifier is strict on all letter characters (a to Z)
-function testStrictLetterShiftModifier(shortcuts) {
+function* testStrictLetterShiftModifier(shortcuts) {
   info("Test strict shift modifier on letters");
   let hitFirst = false;
   let onKey = once(shortcuts, "a", (key, event) => {
     is(event.key, "a");
     ok(!event.altKey);
     ok(!event.ctrlKey);
     ok(!event.metaKey);
     ok(!event.shiftKey);
@@ -268,33 +270,33 @@ function testStrictLetterShiftModifier(s
 
   EventUtils.synthesizeKey(
     "a",
     { shiftKey: false},
     window);
   yield onKey;
 }
 
-function testAltModifier(shortcuts) {
+function* testAltModifier(shortcuts) {
   info("Test Alt modifier");
   let onKey = once(shortcuts, "Alt+F1", (key, event) => {
     is(event.keyCode, window.KeyboardEvent.DOM_VK_F1);
     ok(event.altKey);
     ok(!event.ctrlKey);
     ok(!event.metaKey);
     ok(!event.shiftKey);
   });
   EventUtils.synthesizeKey(
     "VK_F1",
     { altKey: true },
     window);
   yield onKey;
 }
 
-function testCommandOrControlModifier(shortcuts) {
+function* testCommandOrControlModifier(shortcuts) {
   info("Test CommandOrControl modifier");
   let onKey = once(shortcuts, "CommandOrControl+F1", (key, event) => {
     is(event.keyCode, window.KeyboardEvent.DOM_VK_F1);
     ok(!event.altKey);
     if (isOSX) {
       ok(!event.ctrlKey);
       ok(event.metaKey);
     } else {
@@ -325,17 +327,17 @@ function testCommandOrControlModifier(sh
       "VK_F1",
       { ctrlKey: true },
       window);
   }
   yield onKey;
   yield onKeyAlias;
 }
 
-function testCtrlModifier(shortcuts) {
+function* testCtrlModifier(shortcuts) {
   info("Test Ctrl modifier");
   let onKey = once(shortcuts, "Ctrl+F1", (key, event) => {
     is(event.keyCode, window.KeyboardEvent.DOM_VK_F1);
     ok(!event.altKey);
     ok(event.ctrlKey);
     ok(!event.metaKey);
     ok(!event.shiftKey);
   });
@@ -349,17 +351,17 @@ function testCtrlModifier(shortcuts) {
   EventUtils.synthesizeKey(
     "VK_F1",
     { ctrlKey: true },
     window);
   yield onKey;
   yield onKeyAlias;
 }
 
-function testCmdShiftShortcut(shortcuts) {
+function* testCmdShiftShortcut(shortcuts) {
   if (!isOSX) {
     // This test is OSX only (Bug 1300458).
     return;
   }
 
   let onCmdKey = once(shortcuts, "CmdOrCtrl+[", (key, event) => {
     is(event.key, "[");
     ok(!event.altKey);
@@ -383,17 +385,17 @@ function testCmdShiftShortcut(shortcuts)
     "[",
     { metaKey: true },
     window);
 
   yield onCmdKey;
   yield onCmdShiftKey;
 }
 
-function testTarget() {
+function* testTarget() {
   info("Test KeyShortcuts with target argument");
 
   let target = document.createElementNS("http://www.w3.org/1999/xhtml",
     "input");
   document.documentElement.appendChild(target);
   target.focus();
 
   let shortcuts = new KeyShortcuts({