Fix a couple of scroll-related issues:

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 567 matching lines @@
   remoting.fullscreen.activate(
       false,
       function() {
         remoting.fullscreen.removeListener(listener);
       });
   if (remoting.windowFrame) {
     remoting.windowFrame.setClientSession(null);
   } else {
     remoting.toolbar.setClientSession(null);
   }
+  document.body.classList.remove('connected');

[Jamie, 2014/08/23 00:12:00]

This class was previously only used to control aspects of the window frame and
so was managed by that class. It makes more sense to manage it at a higher
level.

 
   // Remove mediasource-rendering class from the container - this will also
   // hide the <video> element.
   this.container_.classList.remove('mediasource-rendering');
 
   this.container_.removeEventListener('mousemove',
                                       this.updateMouseCursorPosition_,
                                       true);
 };
 
@@ skipping 367 matching lines @@
                                           window.devicePixelRatio);
     }
     // Activate full-screen related UX.
     remoting.fullscreen.addListener(this.callOnFullScreenChanged_);
     remoting.fullscreen.syncWithMaximize(true);
     if (remoting.windowFrame) {
       remoting.windowFrame.setClientSession(this);
     } else {
       remoting.toolbar.setClientSession(this);
     }
+    document.body.classList.add('connected');
 
     this.container_.addEventListener('mousemove',
                                      this.updateMouseCursorPosition_,
                                      true);
 
   } else if (status == remoting.ClientSession.State.FAILED) {
     switch (error) {
       case remoting.ClientSession.ConnectionError.HOST_IS_OFFLINE:
         this.error_ = remoting.Error.HOST_IS_OFFLINE;
         break;
@@ skipping 547 matching lines @@
  * @return {{top: number, left:number}} The top-left corner of the plugin.
  */
 remoting.ClientSession.prototype.getPluginPositionForTesting = function() {
   var plugin = this.plugin_.element();
   var style = plugin.style;
   return {
     top: parseFloat(style.marginTop),
     left: parseFloat(style.marginLeft)
   };
 };