[Android] Allow redundant |StartObservingRootWindow()| calls

content/browser/renderer_host/render_widget_host_view_android.cc

 // 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.
 
 #include "content/browser/renderer_host/render_widget_host_view_android.h"
 
 #include <android/bitmap.h>
 
 #include "base/android/build_info.h"
 #include "base/basictypes.h"
@@ skipping 1246 matching lines @@
   outstanding_vsync_requests_ |= requests;
   // Note that if we're not currently observing the root window, outstanding
   // vsync requests will be pushed if/when we resume observing in
   // |StartObservingRootWindow()|.
   if (observing_root_window_ && should_request_vsync)
     content_view_core_->GetWindowAndroid()->RequestVSyncUpdate();
 }
 
 void RenderWidgetHostViewAndroid::StartObservingRootWindow() {
   DCHECK(content_view_core_);
-  DCHECK(!observing_root_window_);
+  if (observing_root_window_)
+    return;
+
   observing_root_window_ = true;
   content_view_core_->GetWindowAndroid()->AddObserver(this);
 
   // Clear existing vsync requests to allow a request to the new window.
   uint32 outstanding_vsync_requests = outstanding_vsync_requests_;
   outstanding_vsync_requests_ = 0;
   RequestVSyncUpdate(outstanding_vsync_requests);
 }
 
 void RenderWidgetHostViewAndroid::StopObservingRootWindow() {
@@ skipping 545 matching lines @@
   results->orientationAngle = display.RotationAsDegree();
   results->orientationType =
       RenderWidgetHostViewBase::GetOrientationTypeForMobile(display);
   gfx::DeviceDisplayInfo info;
   results->depth = info.GetBitsPerPixel();
   results->depthPerComponent = info.GetBitsPerComponent();
   results->isMonochrome = (results->depthPerComponent == 0);
 }
 
 } // namespace content