Avoid DCHECK when installing a theme with non-opaque NTP bg color.

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/render_widget_host_view.h"
 #include "content/public/browser/web_contents.h"
@@ skipping 40 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%
-  const SkColor ntp_background =
-      theme->GetColor(ThemeProperties::COLOR_NTP_BACKGROUND);
+  // Make sure the background is opaque.
+  const SkColor ntp_background = color_utils::GetResultingPaintColor(
+      theme->GetColor(ThemeProperties::COLOR_NTP_BACKGROUND), SK_ColorWHITE);
   set_background(views::Background::CreateSolidBackground(
       SkColorGetR(ntp_background) * kBackgroundBrightness / 0xFF,
       SkColorGetG(ntp_background) * kBackgroundBrightness / 0xFF,
       SkColorGetB(ntp_background) * kBackgroundBrightness / 0xFF,
       SkColorGetA(ntp_background)));

[Peter Kasting, 2017/05/08 23:11:14]

Seems like this SkColorGetA can just become SK_AlphaOPAQUE.

[Evan Stade, 2017/05/09 14:14:31]

It could. I considered it. Which is more correct/readable? I dunno. I erred on
the side of not having this line assume something about the previous line.

 
 
   if (web_contents()) {
     content::RenderWidgetHostView* rwhv =
         web_contents()->GetRenderWidgetHostView();
     if (rwhv)
      rwhv->SetBackgroundColor(ntp_background);
   }
 }
 
@@ skipping 44 matching lines @@
   cloned_layer_tree_.reset();
   DestroyLayer();
   set_layer_owner_delegate(nullptr);
 }
 
 void ContentsWebView::RenderViewReady() {
   // Apply the theme color to be the default background on startup.
   OnThemeChanged();
   WebView::RenderViewReady();
 }