Set pepper flash fullscreen window to opaque.

content/browser/renderer_host/render_widget_host_view_mac.mm

 // 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_mac.h"
 
 #include <QuartzCore/QuartzCore.h>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 453 matching lines @@
   pepper_fullscreen_window_.reset([[PepperFlashFullscreenWindow alloc]
       initWithContentRect:[screen frame]
                 styleMask:NSBorderlessWindowMask
                   backing:NSBackingStoreBuffered
                     defer:NO]);
   [pepper_fullscreen_window_ setLevel:NSFloatingWindowLevel];
   [pepper_fullscreen_window_ setReleasedWhenClosed:NO];
   [cocoa_view_ setCanBeKeyView:YES];
   [cocoa_view_ setFrame:[[pepper_fullscreen_window_ contentView] bounds]];
   [cocoa_view_ setAutoresizingMask:NSViewWidthSizable | NSViewHeightSizable];
+  // If the pepper fullscreen window isn't opaque then there are performance
+  // issues when it's on the discrete GPU and the Chrome window is being drawn
+  // to. http://crbug.com/171911
+  [pepper_fullscreen_window_ setOpaque:YES];
 
   // Note that this forms a reference cycle between the fullscreen window and
   // the rwhvmac: The PepperFlashFullscreenWindow retains cocoa_view_,
   // but cocoa_view_ keeps pepper_fullscreen_window_ in an instance variable.
   // This cycle is normally broken when -keyEvent: receives an <esc> key, which
   // explicitly calls Shutdown on the render_widget_host_, which calls
   // Destroy() on RWHVMac, which drops the reference to
   // pepper_fullscreen_window_.
   [[pepper_fullscreen_window_ contentView] addSubview:cocoa_view_];
 
@@ skipping 2846 matching lines @@
   if (!string) return NO;
 
   // If the user is currently using an IME, confirm the IME input,
   // and then insert the text from the service, the same as TextEdit and Safari.
   [self confirmComposition];
   [self insertText:string];
   return YES;
 }
 
 @end