[blink] Support (semi-)transparent background colors in WebView/Frame.

third_party/WebKit/Source/web/WebPagePopupImpl.cpp

 /*
  * Copyright (C) 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 295 matching lines @@
 
   provideContextFeaturesTo(*m_page, WTF::makeUnique<PagePopupFeaturesClient>());
   DEFINE_STATIC_LOCAL(LocalFrameClient, emptyLocalFrameClient,
                       (EmptyLocalFrameClient::create()));
   LocalFrame* frame = LocalFrame::create(&emptyLocalFrameClient, m_page, 0);
   frame->setPagePopupOwner(m_popupClient->ownerElement());
   frame->setView(FrameView::create(*frame));
   frame->init();
   frame->view()->setParentVisible(true);
   frame->view()->setSelfVisible(true);
-  frame->view()->setTransparent(false);
   if (AXObjectCache* cache =
           m_popupClient->ownerElement().document().existingAXObjectCache())
     cache->childrenChanged(&m_popupClient->ownerElement());
 
   DCHECK(frame->domWindow());
   PagePopupSupplement::install(*frame, *this, m_popupClient);
   DCHECK_EQ(m_popupClient->ownerElement().document().existingAXObjectCache(),
             frame->document()->existingAXObjectCache());
 
   initializeLayerTreeView();
@@ skipping 261 matching lines @@
   // A WebPagePopupImpl instance usually has two references.
   //  - One owned by the instance itself. It represents the visible widget.
   //  - One owned by a WebViewImpl. It's released when the WebViewImpl ask the
   //    WebPagePopupImpl to close.
   // We need them because the closing operation is asynchronous and the widget
   // can be closed while the WebViewImpl is unaware of it.
   return adoptRef(new WebPagePopupImpl(client)).leakRef();
 }
 
 }  // namespace blink