Add setVisibilityState API to WebFrameWidget

Source/web/WebFrameWidgetImpl.cpp

 /*
  * Copyright (C) 2014 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 996 matching lines @@
             m_layerTreeView->registerViewportLayers(nullptr, pageScaleLayer, rootScrollLayer->platformLayer(), nullptr);
         } else {
             m_layerTreeView->clearRootLayer();
             m_layerTreeView->clearViewportLayers();
         }
     }
 
     suppressInvalidations(false);
 }
 
+void WebFrameWidgetImpl::setVisibilityState(WebPageVisibilityState visibilityState, bool isInitialState)
+{
+    if (!m_page)
+        return;
+
+    ASSERT(visibilityState == WebPageVisibilityStateVisible || visibilityState == WebPageVisibilityStateHidden || visibilityState == WebPageVisibilityStatePrerender);

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

I guess the original implementation has this, but this assert seems unnecessary.
Do we usually assert on things like this? This assert just contains all the
valid enum values, which is what I would have expected to begin with =)

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

I think it is just a guard. Looks like brettw originally suggested it, in a
review 4 years ago, and was intended to substitute for a switch.

+    m_page->setVisibilityState(static_cast<PageVisibilityState>(static_cast<int>(visibilityState)), isInitialState);

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

Can we just static_cast<> directly to PageVisibilityState here?

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

Apparently we can. Looks like on oversight in the original code.

+
+    if (m_layerTreeView) {
+        bool visible = visibilityState == WebPageVisibilityStateVisible;
+        m_layerTreeView->setVisible(visible);
+    }
+}
+
 } // namespace blink