Eat all keys involving Search when ChromeVox is on and add a pass through mode command.

chrome/browser/resources/chromeos/chromevox/cvox2/background/background.js

 // Copyright 2014 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.
 
 /**
  * @fileoverview The entry point for all ChromeVox2 related code for the
  * background page.
  */
 
 goog.provide('Background');
@@ skipping 98 matching lines @@
       return localStorage['active'] !== 'false';
     },
     set: function(value) {
       localStorage['active'] = value;
     }
   });
 
   cvox.ExtensionBridge.addMessageListener(this.onMessage_);
 
   document.addEventListener('keydown', this.onKeyDown.bind(this), true);
+  document.addEventListener('keyup', this.onKeyUp.bind(this), true);
   cvox.ChromeVoxKbHandler.commandHandler = this.onGotCommand.bind(this);
 
   // Classic keymap.
   cvox.ChromeVoxKbHandler.handlerKeyMap = cvox.KeyMap.fromDefaults();
 
   // Live region handler.
   this.liveRegions_ = new LiveRegions(this);
 
+  /** @type {number} @private */
+  this.passThroughKeyUpCount_ = 0;
+
   if (!chrome.accessibilityPrivate.setKeyboardListener)
     chrome.accessibilityPrivate.setKeyboardListener = function() {};
 };
 
 Background.prototype = {
   __proto__: ChromeVoxState.prototype,
 
   /**
    * @override
    */
@@ skipping 332 matching lines @@
       case 'toggleStickyMode':
         cvox.ChromeVoxBackground.setPref('sticky',
                                          !cvox.ChromeVox.isStickyPrefOn,
                                          true);
 
         if (cvox.ChromeVox.isStickyPrefOn)
           chrome.accessibilityPrivate.setKeyboardListener(true, true);
         else
           chrome.accessibilityPrivate.setKeyboardListener(true, false);
         return false;
+      case 'passThroughMode':
+        cvox.ChromeVox.passThroughMode = true;
+        cvox.ChromeVox.tts.speak(
+            Msgs.getMsg('pass_through_key'), cvox.QueueMode.QUEUE);
+        return true;
       default:
         return true;
     }
 
     if (pred) {
       var node = AutomationUtil.findNextNode(
           current.getBound(dir).node, dir, pred);
 
       if (node) {
         current = cursors.Range.fromNode(node);
@@ skipping 29 matching lines @@
     return false;
   },
 
   /**
    * Handles key down events.
    * @param {Event} evt The key down event to process.
    * @return {boolean} True if the default action should be performed.
    */
   onKeyDown: function(evt) {
     evt.stickyMode = cvox.ChromeVox.isStickyModeOn() && cvox.ChromeVox.isActive;
+    if (cvox.ChromeVox.passThroughMode)
+      return false;
+
     if (this.mode_ != ChromeVoxMode.CLASSIC &&
         !cvox.ChromeVoxKbHandler.basicKeyDownActionsListener(evt)) {
       evt.preventDefault();
       evt.stopPropagation();
     }
+    Output.flushNextSpeechUtterance();
+  },
 
-    Output.flushNextSpeechUtterance();
+  /**
+   * Handles key up events.
+   * @param {Event} evt The key down event to process.
+   * @return {boolean} True if the default action should be performed.
+   */
+  onKeyUp: function(evt) {
+    // Reset pass through mode once a keyup (not involving the pass through key)
+    // is seen. The pass through command involves three keys.
+    if (cvox.ChromeVox.passThroughMode) {
+      if (this.passThroughKeyUpCount_ >= 3) {
+        cvox.ChromeVox.passThroughMode = false;
+        this.passThroughKeyUpCount_ = 0;
+      } else {
+        this.passThroughKeyUpCount_++;
+      }
+    }
   },
 
   /**
    * Open the options page in a new tab.
    */
   showOptionsPage: function() {
     var optionsPage = {url: 'chromevox/background/options.html'};
     chrome.tabs.create(optionsPage);
   },
 
@@ skipping 150 matching lines @@
     return glob.replace(/[.+^$(){}|[\]\\]/g, '\\$&')
         .replace(/\*/g, '.*')
         .replace(/\?/g, '.');
   }).join('|') + ')$');
 };
 
 /** @type {Background} */
 global.backgroundObj = new Background();
 
 });  // goog.scope