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

third_party/WebKit/Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 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 3505 matching lines @@
   // Set any existing frames to be transparent.
   Frame* frame = m_page->mainFrame();
   while (frame) {
     if (frame->isLocalFrame())
       toLocalFrame(frame)->view()->setTransparent(isTransparent);
     frame = frame->tree().traverseNext();
   }
 
   // Future frames check this to know whether to be transparent.
   m_isTransparent = isTransparent;
-
-  if (m_layerTreeView)
-    m_layerTreeView->setHasTransparentBackground(this->isTransparent());
+  updateLayerTreeBackgroundColor();
 }
 
 bool WebViewImpl::isTransparent() const {
   return m_isTransparent;
 }
 
 WebInputMethodControllerImpl* WebViewImpl::getActiveWebInputMethodController()
     const {
   return WebInputMethodControllerImpl::fromFrame(focusedLocalFrameInWidget());
 }
@@ skipping 468 matching lines @@
     return;
 
   m_layerTreeView->setPageScaleFactorAndLimits(
       pageScaleFactor(), minimumPageScaleFactor(), maximumPageScaleFactor());
 }
 
 void WebViewImpl::updateLayerTreeBackgroundColor() {
   if (!m_layerTreeView)
     return;
 
-  m_layerTreeView->setBackgroundColor(alphaChannel(m_backgroundColorOverride)
-                                          ? m_backgroundColorOverride
-                                          : backgroundColor());
+  WebColor color = alphaChannel(m_backgroundColorOverride)
+                       ? m_backgroundColorOverride
+                       : backgroundColor();
+  m_layerTreeView->setBackgroundColor(color);
+  m_layerTreeView->setHasTransparentBackground(alphaChannel(color) <

[dgozman, 2017/03/01 19:11:52]

Similarly to Chris' question, do we actually need two methods here if we always
pass the background color and layer tree view can reason on it's transparency?

[Eric Seckler, 2017/03/07 18:00:47]

Implemented as suggested.

+                                               SK_AlphaOPAQUE);
 }
 
 void WebViewImpl::updateLayerTreeDeviceScaleFactor() {
   DCHECK(page());
   DCHECK(m_layerTreeView);
 
   float deviceScaleFactor = m_compositorDeviceScaleFactorOverride
                                 ? m_compositorDeviceScaleFactorOverride
                                 : page()->deviceScaleFactorDeprecated();
   m_layerTreeView->setDeviceScaleFactor(deviceScaleFactor);
@@ skipping 133 matching lines @@
   if (focusedFrame->localFrameRoot() != mainFrameImpl()->frame())
     return nullptr;
   return focusedFrame;
 }
 
 LocalFrame* WebViewImpl::focusedLocalFrameAvailableForIme() const {
   return m_imeAcceptEvents ? focusedLocalFrameInWidget() : nullptr;
 }
 
 }  // namespace blink