Add occlusion support to WebContentsImpl and RenderWidgetHostView

content/browser/web_contents/web_contents_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.
 
 #import <Carbon/Carbon.h>
 
 #import "content/browser/web_contents/web_contents_view_mac.h"
 
 #include <string>
 
@@ skipping 588 matching lines @@
 
 - (void)viewWillMoveToWindow:(NSWindow*)newWindow {
   NSWindow* oldWindow = [self window];
 
   NSNotificationCenter* notificationCenter =
       [NSNotificationCenter defaultCenter];
 
   // Occlusion notification APIs are new in Mavericks.
   bool supportsOcclusionAPIs = base::mac::IsOSMavericksOrLater();
 
-  // Use of occlusion APIs is causing bugs:
-  // http://crbug.com/430968: focus set incorrectly.
-  // http://crbug.com/431272: flashes of incorrect content.
-  // http://crbug.com/310374: white flashes (comment 22).
-  supportsOcclusionAPIs = false;
-
   if (supportsOcclusionAPIs) {
     if (oldWindow) {
       [notificationCenter
           removeObserver:self
                     name:NSWindowDidChangeOcclusionStateNotification
                   object:oldWindow];
     }
     if (newWindow) {
       [notificationCenter
           addObserver:self
              selector:@selector(windowChangedOcclusionState:)
                  name:NSWindowDidChangeOcclusionStateNotification
                object:newWindow];
     }
   }
 }
 
 - (void)windowChangedOcclusionState:(NSNotification*)notification {
   DCHECK(base::mac::IsOSMavericksOrLater());
   NSWindow* window = [notification object];
   WebContentsImpl* webContents = [self webContents];
   if (window && webContents) {
     if ([window occlusionState] & NSWindowOcclusionStateVisible) {
-      if (!webContents->should_normally_be_visible())
-        webContents->WasShown();
+      webContents->WasUnOccluded();
     } else {
-      if (webContents->should_normally_be_visible())
-        webContents->WasHidden();
+      webContents->WasOccluded();
     }
   }
 }
 
 @end