Add setVisibilityState API to WebFrameWidget

public/web/WebFrameWidget.h

Index: public/web/WebFrameWidget.h
diff --git a/public/web/WebFrameWidget.h b/public/web/WebFrameWidget.h
index 3fa72a339e0e914cfe4f7a4da9a99b37e0da3b1d..b9411564f2227b326f998e2c6b4e85719647a635 100644
--- a/public/web/WebFrameWidget.h
+++ b/public/web/WebFrameWidget.h
@@ -32,6 +32,7 @@
 #define WebFrameWidget_h
 
 #include "../platform/WebCommon.h"
+#include "../platform/WebPageVisibilityState.h"
 #include "public/web/WebWidget.h"
 
 namespace blink {
@@ -42,6 +43,11 @@ class WebWidgetClient;
 class WebFrameWidget : public WebWidget {
 public:
     BLINK_EXPORT static WebFrameWidget* create(WebWidgetClient*, WebLocalFrame*);
+
+    // Set frame-level visibility state.

[dcheng, 2015/02/26 17:42:08]

So this says frame-level state, but the enum is called page visibility state. I
think this comment should be updated to describe how the whole page visibility
thing works in conjunction with OOPIF, and why this is needed.

[kenrb, 2015/02/26 18:08:52]

Done.

+    // FIXME: Is this necessary? Should WebViewImpl::setVisibilityState() somehow
+    // trickle down this notification instead?

[dcheng, 2015/02/26 17:42:08]

I think this FIXME is unnecessary.

[kenrb, 2015/02/26 18:08:52]

Ok. I think we need to invest some time to understand how visibility would work
better, but probably better just to file a bug.

+    virtual void setVisibilityState(WebPageVisibilityState visibilityState, bool isInitialState) { }
 };
 
 } // namespace blink