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

third_party/WebKit/Source/web/WebViewImpl.cpp

Index: third_party/WebKit/Source/web/WebViewImpl.cpp
diff --git a/third_party/WebKit/Source/web/WebViewImpl.cpp b/third_party/WebKit/Source/web/WebViewImpl.cpp
index 945f27e4c99ab304fcb214c84680cb17730107fd..d6496bcdc611f8f6ea3844548d03a48ce06d9729 100644
--- a/third_party/WebKit/Source/web/WebViewImpl.cpp
+++ b/third_party/WebKit/Source/web/WebViewImpl.cpp
@@ -3523,9 +3523,7 @@ void WebViewImpl::setIsTransparent(bool isTransparent) {
 
   // 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 {
@@ -4014,9 +4012,12 @@ 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() {