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

In ChromeVox Next, Search+Shift+Esc activates pass through mode. The subsequent key will be passed through directly to the system. In particular, the key needs to be a ChromeVox command. For example, Search+Shift+Esc followed by any number of key (e.g. Ctrl+L), then ended by Search+L would result in the screen locking since the passed through key is the last ChromeVox command.

This cl also makes all key events involving Search captured.

TEST=hit Search+L. Verify the key gets eaten (no screen lock) and ChromeVox tries to move to the next link.
Press Search+Shift+Esc; then Search+L. Verify screen locks.
Do the same with sticky mode on. Double tap Search. Press Shift+Esc. Verify pass through activates. Press Search+L and see that screen locks.

Review URL: https://codereview.chromium.org/1636243002

Cr-Commit-Position: refs/heads/master@{#372205}

chrome/browser/chromeos/accessibility/spoken_feedback_event_rewriter.cc

@@ -53,6 +53,9 @@ bool SpokenFeedbackEventRewriterDelegate::DispatchKeyEventToChromeVox(
 
   content::RenderViewHost* rvh = host->render_view_host();
 
+  // Always capture the Search key.
+  capture |= key_event.IsCommandDown();
+
   // Listen for any unhandled keyboard events from ChromeVox's background page
   // when capturing keys to reinject.
   if (capture)

chrome/browser/resources/chromeos/chromevox/chromevox/background/keymaps/next_keymap.json

@@ -339,6 +339,16 @@
         },
         "platformFilter": 10
       }
+    },
+    {
+      "command": "passThroughMode",
+      "sequence": {
+        "cvoxModifier": true,
+        "keys": {
+          "keyCode": [27],
+          "shiftKey": [true]
+        }
+      }
     }
   ]
 }

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

@@ -116,6 +116,7 @@ Background = function() {
   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.
@@ -124,6 +125,9 @@ Background = function() {
   // Live region handler.
   this.liveRegions_ = new LiveRegions(this);
 
+  /** @type {number} @private */
+  this.passThroughKeyUpCount_ = 0;
+
   if (!chrome.accessibilityPrivate.setKeyboardListener)
     chrome.accessibilityPrivate.setKeyboardListener = function() {};
 };
@@ -476,6 +480,11 @@ Background.prototype = {
         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;
     }
@@ -525,15 +534,35 @@ Background.prototype = {
    */
   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();
   },
 
+  /**
+   * 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.
    */