Restore focus when an automation node becomes invalidated.

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 262 matching lines @@
     return this.currentRange_;
   },
 
   /**
    * @override
    */
   setCurrentRange: function(newRange) {
     if (!newRange)
       return;
 
+    // Is the range invalid?
+    if (newRange.start.node.role === undefined ||

[dmazzoni, 2016/03/16 23:48:36]

Consider ending an excursion if necessary?

[David Tseng, 2016/03/17 00:40:11]

I don't think we want this. For example, in an incremental search, if we
navigate to an element that gets destroyed after we set it as a current range,
we still want to stay in excursion, but just move somewhere valid.

+        newRange.end.node.role === undefined) {
+      // Restore range to the focused location.
+      chrome.automation.getFocus(function(f) {
+        newRange = cursors.Range.fromNode(f);
+      });
+    }
+
     if (!this.inExcursion_)
       this.savedRange_ = new cursors.Range(newRange.start, newRange.end);
 
     this.currentRange_ = newRange;
 
     if (this.currentRange_)
       this.currentRange_.start.node.makeVisible();
   },
 
   /** Forces ChromeVox Next to be active for all tabs. */
@@ skipping 703 matching lines @@
     return glob.replace(/[.+^$(){}|[\]\\]/g, '\\$&')
         .replace(/\*/g, '.*')
         .replace(/\?/g, '.');
   }).join('|') + ')$');
 };
 
 /** @type {Background} */
 global.backgroundObj = new Background();
 
 });  // goog.scope