Fire visibilityChange event on out-of-process iframes.

third_party/WebKit/public/web/WebFrameClient.h

Index: third_party/WebKit/public/web/WebFrameClient.h
diff --git a/third_party/WebKit/public/web/WebFrameClient.h b/third_party/WebKit/public/web/WebFrameClient.h
index 497364f2c4a8d766800e13819bcbab489ed03925..9984070eb3d09df049b4c8ef3ffa2b61e272d370 100644
--- a/third_party/WebKit/public/web/WebFrameClient.h
+++ b/third_party/WebKit/public/web/WebFrameClient.h
@@ -51,6 +51,7 @@
 #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"
@@ -710,6 +711,14 @@ public:
     // Mojo ----------------------------------------------------------------
     virtual ServiceRegistry* serviceRegistry() { return nullptr; }
 
+    // Visibility ----------------------------------------------------------
+
+    // Returns the current visibility of the WebFrame.
+    virtual WebPageVisibilityState visibilityState() const
+    {
+        return WebPageVisibilityStateVisible;
+    }
+
 protected:
     virtual ~WebFrameClient() { }
 };