Fix the problem that releasing a key after pressing multiple modifiers corrupts keyboard overlay

chrome/browser/resources/keyboard_overlay.js

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 var BASE_KEYBOARD = {
   top: 0,
   left: 0,
   width: 1237,
   height: 514
 };
@@ skipping 102 matching lines @@
   return result;
 }
 
 /**
  * Returns a list of modifiers from the key event.
  */
 function getModifiers(e) {
   if (!e) {
     return [];
   }
-  var modifiers = [];
-  if (e.keyCode == 16 || e.shiftKey) {
-    modifiers.push('SHIFT');
+  var isKeyDown = (e.type == 'keydown');
+  var keyCodeToModifier = {16: 'SHIFT', 17: 'CTRL', 18: 'ALT'};
+  var modifierWithKeyCode = keyCodeToModifier[e.keyCode];
+  var isPressed = {'SHIFT': e.shiftKey, 'CTRL': e.ctrlKey, 'ALT': e.altKey};
+  // if e.keyCode is one of Shift, Ctrl and Alt, isPressed should
+  // be changed because the key currently pressed
+  // does not affect the values of e.shiftKey, e.ctrlKey and e.altKey
+  if(modifierWithKeyCode){
+    isPressed[modifierWithKeyCode] = isKeyDown;
   }
-  if (e.keyCode == 17 || e.ctrlKey) {
-    modifiers.push('CTRL');
-  }
-  if (e.keyCode == 18 || e.altKey) {
-    modifiers.push('ALT');
-  }
-  return modifiers.sort();
+  // make the result array
+  return ['SHIFT', 'CTRL', 'ALT'].filter(
+      function(modifier) {
+        return isPressed[modifier];
+      }).sort();
 }
 
 /**
  * Returns an ID of the key.
  */
 function keyId(identifier, i) {
   return identifier + '-key-' + i;
 }
 
 /**
@@ skipping 114 matching lines @@
     if (pos && pos.length > 0) {
       chars.push(hex2char(pos));
     }
   }
   return chars.join(' ');
 }
 
 /**
  * Updates the whole keyboard.
  */
-function update(e) {
-  var modifiers = getModifiers(e);
+function update(modifiers) {
   var instructions = document.getElementById('instructions');
   if (modifiers.length == 0) {
     instructions.style.visibility = 'visible';
   } else {
     instructions.style.visibility = 'hidden';
   }
 
   var keyboardGlyphData = getKeyboardGlyphData();
   var shortcutData = getShortcutData();
   var layout = getLayouts()[keyboardGlyphData.layoutName];
@@ skipping 35 matching lines @@
       var format = keyData.format;
       if (format == 'left' || format == 'right') {
         shortcutText.style.textAlign = format;
         keyText.style.textAlign = format;
       }
     }
   }
 }
 
 /**
- * A callback furnction for the onkeydown event.
+ * A callback function for onkeydown and onkeyup events.
  */
-function keydown(e) {
+function handleKeyEvent(e){
+  var modifiers = getModifiers(e);
   if (!getKeyboardOverlayId()) {
     return;
   }
-  update(e);
+  update(modifiers);
 }
 
 /**
- * A callback furnction for the onkeyup event.
- */
-function keyup(e) {
-  if (!getKeyboardOverlayId()) {
-    return;
-  }
-  update();
-}
-
-/**
  * Initializes the layout of the keys.
  */
 function initLayout() {
   var layout = getLayouts()[getKeyboardGlyphData().layoutName];
   var keyboard = document.body;
   var minX = window.innerWidth;
   var maxX = 0;
   var minY = window.innerHeight;
   var maxY = 0;
   var multiplier = 1.38 * window.innerWidth / BASE_KEYBOARD.width;
@@ skipping 62 matching lines @@
   instructionsHideText.className = 'keyboard-overlay-instructions-hide-text';
   instructionsHideText.innerHTML = templateData.keyboardOverlayInstructionsHide;
   instructions.appendChild(instructionsHideText);
   keyboard.appendChild(instructions);
 }
 
 /**
  * A callback function for the onload event of the body element.
  */
 function init() {
-  document.addEventListener('keydown', keydown);
-  document.addEventListener('keyup', keyup);
+  document.addEventListener('keydown', handleKeyEvent);
+  document.addEventListener('keyup', handleKeyEvent);
   chrome.send('getKeyboardOverlayId');
 }
 
 /**
  * Initializes the global keyboad overlay ID and the layout of keys.
  * Called after sending the 'getKeyboardOverlayId' message.
  */
 function initKeyboardOverlayId(overlayId) {
   // Libcros returns an empty string when it cannot find the keyboard overlay ID
   // corresponding to the current input method.
   // In such a case, fallback to the default ID (en_US).
   if (overlayId) {
     keyboardOverlayId = overlayId;
   }
   while(document.body.firstChild) {
     document.body.removeChild(document.body.firstChild);
   }
   initLayout();
   update();
 }
 
 document.addEventListener('DOMContentLoaded', init);