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

third_party/WebKit/Source/platform/testing/WebLayerTreeViewImplForTesting.cpp

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "platform/testing/WebLayerTreeViewImplForTesting.h"
 
 #include "base/threading/thread_task_runner_handle.h"
 #include "cc/animation/animation_host.h"
 #include "cc/animation/animation_timeline.h"
 #include "cc/blink/web_layer_impl.h"
@@ skipping 74 matching lines @@
                  m_layerTreeHost->device_viewport_size().height());
 }
 
 void WebLayerTreeViewImplForTesting::setDeviceScaleFactor(
     float deviceScaleFactor) {
   m_layerTreeHost->SetDeviceScaleFactor(deviceScaleFactor);
 }
 
 void WebLayerTreeViewImplForTesting::setBackgroundColor(WebColor color) {
   m_layerTreeHost->set_background_color(color);
-}
-
-void WebLayerTreeViewImplForTesting::setHasTransparentBackground(
-    bool transparent) {
-  m_layerTreeHost->set_has_transparent_background(transparent);
+  m_layerTreeHost->set_has_transparent_background(SkColorGetA(color) <
+                                                  SK_AlphaOPAQUE);
 }
 
 void WebLayerTreeViewImplForTesting::setVisible(bool visible) {
   m_layerTreeHost->SetVisible(visible);
 }
 
 void WebLayerTreeViewImplForTesting::setPageScaleFactorAndLimits(
     float pageScaleFactor,
     float minimum,
     float maximum) {
@@ skipping 94 matching lines @@
 void WebLayerTreeViewImplForTesting::setHaveScrollEventHandlers(
     bool haveEentHandlers) {
   m_layerTreeHost->SetHaveScrollEventHandlers(haveEentHandlers);
 }
 
 bool WebLayerTreeViewImplForTesting::haveScrollEventHandlers() const {
   return m_layerTreeHost->have_scroll_event_handlers();
 }
 
 }  // namespace blink