Allow to have a transparent UA dependent background.

chrome/browser/ui/views/frame/contents_web_view.cc

 // Copyright 2014 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 "chrome/browser/ui/views/frame/contents_web_view.h"
 
 #include "chrome/browser/themes/theme_properties.h"
 #include "chrome/browser/ui/views/status_bubble_views.h"
 #include "content/public/browser/web_contents.h"
 #include "ui/base/theme_provider.h"
@@ skipping 39 matching lines @@
 void ContentsWebView::OnThemeChanged() {
   const ui::ThemeProvider* const theme = GetThemeProvider();
   if (!theme)
     return;
 
   // Set the background color to a dark tint of the new tab page's background
   // color.  This is the color filled within the WebView's bounds when its child
   // view is sized specially for fullscreen tab capture.  See WebView header
   // file comments for more details.
   const int kBackgroundBrightness = 0x33;  // 20%
+  // FIXME: Clear alpha only upon a call to
+  // content::RenderWidgetHostView->SetBackgroundColor(SK_ColorTRANSPARENT).
   const SkColor ntp_background =
-      theme->GetColor(ThemeProperties::COLOR_NTP_BACKGROUND);
+      theme->GetColor(ThemeProperties::COLOR_NTP_BACKGROUND) & 0x00FFFFFF;

[trchen, 2016/02/25 02:30:12]

ditto.

[Julien Isorce Samsung, 2016/02/25 11:33:55]

Same

   set_background(views::Background::CreateSolidBackground(
       SkColorGetR(ntp_background) * kBackgroundBrightness / 0xFF,
       SkColorGetG(ntp_background) * kBackgroundBrightness / 0xFF,
       SkColorGetB(ntp_background) * kBackgroundBrightness / 0xFF,
       SkColorGetA(ntp_background)));
 }
 
 void ContentsWebView::OnLayerRecreated(ui::Layer* old_layer,
                                        ui::Layer* new_layer) {
   if (!cloned_layer_tree_)
@@ skipping 35 matching lines @@
   cloned_layer_tree_->root()->SetBounds(
       gfx::Rect(origin, cloned_layer_tree_->root()->bounds().size()));
   layer()->Add(cloned_layer_tree_->root());
 }
 
 void ContentsWebView::DestroyClonedLayer() {
   cloned_layer_tree_.reset();
   SetPaintToLayer(false);
   set_layer_owner_delegate(nullptr);
 }