Fire visibilityChange event on out-of-process iframes.

content/public/renderer/render_frame.h

Index: content/public/renderer/render_frame.h
diff --git a/content/public/renderer/render_frame.h b/content/public/renderer/render_frame.h
index a44ef557be96c35b00d7cc565b18d384b33c2521..47b958db2ac001c1d0ebfa38c9b6f72ae9002c88 100644
--- a/content/public/renderer/render_frame.h
+++ b/content/public/renderer/render_frame.h
@@ -15,6 +15,7 @@
 #include "content/public/common/console_message_level.h"
 #include "ipc/ipc_listener.h"
 #include "ipc/ipc_sender.h"
+#include "third_party/WebKit/public/platform/WebPageVisibilityState.h"
 #include "third_party/WebKit/public/web/WebNavigationPolicy.h"
 
 class GURL;
@@ -214,6 +215,9 @@ class CONTENT_EXPORT RenderFrame : public IPC::Listener,
   // Whether or not this frame is currently pasting.
   virtual bool IsPasting() const = 0;
 
+  // Returns the current visibility of the frame.
+  virtual blink::WebPageVisibilityState GetVisibilityState() const = 0;
+
  protected:
   ~RenderFrame() override {}