Fire visibilityChange event on out-of-process iframes.

third_party/WebKit/public/web/WebFrameClient.h

 /*
  * Copyright (C) 2011, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 33 matching lines @@
 #include "WebNavigationType.h"
 #include "WebNavigatorContentUtilsClient.h"
 #include "WebSandboxFlags.h"
 #include "WebTextDirection.h"
 #include "public/platform/BlameContext.h"
 #include "public/platform/WebCommon.h"
 #include "public/platform/WebEffectiveConnectionType.h"
 #include "public/platform/WebFileSystem.h"
 #include "public/platform/WebFileSystemType.h"
 #include "public/platform/WebLoadingBehaviorFlag.h"
+#include "public/platform/WebPageVisibilityState.h"
 #include "public/platform/WebSecurityOrigin.h"
 #include "public/platform/WebSetSinkIdCallbacks.h"
 #include "public/platform/WebStorageQuotaCallbacks.h"
 #include "public/platform/WebStorageQuotaType.h"
 #include "public/platform/WebURLError.h"
 #include "public/platform/WebURLRequest.h"
 #include "public/web/WebContentSecurityPolicy.h"
 #include <v8.h>
 
 namespace blink {
@@ skipping 639 matching lines @@
     {
         if (callbacks) {
             callbacks->onError(WebSetSinkIdError::NotSupported);
             delete callbacks;
         }
     }
 
     // Mojo ----------------------------------------------------------------
     virtual ServiceRegistry* serviceRegistry() { return nullptr; }
 
+    // Visibility -----------------------------------------------------------

[kenrb, 2016/05/25 20:29:14]

Nit: there is one more hyphen in this line than the others. :)

[lfg, 2016/05/31 19:54:01]

Done.

+
+    // Returns the current visibility of the WebView.
+    virtual WebPageVisibilityState visibilityState() const
+    {
+        return WebPageVisibilityStateVisible;
+    }
+
 protected:
     virtual ~WebFrameClient() { }
 };
 
 } // namespace blink
 
 #endif