Don't send mouse events if the plugin doesn't have focus.

remoting/webapp/client_session.js

 // Copyright (c) 2012 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
  * Class handling creation and teardown of a remoting client session.
  *
  * The ClientSession class controls lifetime of the client plugin
  * object and provides the plugin with the functionality it needs to
@@ skipping 330 matching lines @@
 
 /**
  * Callback function called when the plugin element loses focus.
  */
 remoting.ClientSession.prototype.pluginLostFocus_ = function() {
   if (this.plugin_) {
     // Release all keys to prevent them becoming 'stuck down' on the host.
     this.plugin_.releaseAllKeys();
     if (this.plugin_.element()) {
       // Focus should stay on the element, not (for example) the toolbar.
-      this.plugin_.element().focus();
+      // Due to crbug.com/246335, we can't restore the focus immediately,
+      // otherwise the plugin gets confused about whether or not it has focus.
+      window.setTimeout(
+          this.plugin_.element().focus.bind(this.plugin_.element()),
+          0);

[weitao, 2014/02/07 23:54:23]

Nice trick. :)

     }
   }
 };
 
 /**
  * Adds <embed> element to |container| and readies the sesion object.
  *
  * @param {Element} container The element to add the plugin to.
  * @param {function(string, string):boolean} onExtensionMessage The handler for
  *     protocol extension messages. Returns true if a message is recognized;
@@ skipping 991 matching lines @@
  * Sends a clipboard item to the host.
  *
  * @param {string} mimeType The MIME type of the clipboard item.
  * @param {string} item The clipboard item.
  */
 remoting.ClientSession.prototype.sendClipboardItem = function(mimeType, item) {
   if (!this.plugin_)
     return;
   this.plugin_.sendClipboardItem(mimeType, item)
 };