Avoid getting stuck when calling focus() on iframe nodes.

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 482 matching lines @@
         }
         return false;
       }
     }
 
     if (current) {
       // TODO(dtseng): Figure out what it means to focus a range.
       var actionNode = current.start.node;
       if (actionNode.role == RoleType.inlineTextBox)
         actionNode = actionNode.parent;
-      actionNode.focus();
+
+      // Iframes, when focused, causes the child webArea to fire focus event.
+      // This can result in getting stuck when navigating backward.
+      if (!actionNode.role == RoleType.iframe && actionNode.state.focused)

[dmazzoni, 2016/01/23 00:01:38]

The order of precedence isn't obvious to me here, could you either put the thing
being negated in parens, or use a != operator?

[David Tseng, 2016/01/25 20:13:16]

Done.

+        actionNode.focus();
 
       var prevRange = this.currentRange_;
       this.setCurrentRange(current);
 
       new Output().withSpeechAndBraille(
               this.currentRange_, prevRange, Output.EventType.NAVIGATE)
           .withQueueMode(cvox.QueueMode.FLUSH)
           .go();
     }
 
@@ skipping 176 matching lines @@
     return glob.replace(/[.+^$(){}|[\]\\]/g, '\\$&')
         .replace(/\*/g, '.*')
         .replace(/\?/g, '.');
   }).join('|') + ')$');
 };
 
 /** @type {Background} */
 global.backgroundObj = new Background();
 
 });  // goog.scope