Query the preferred readback config in CopyFromBackingStore

chrome/browser/thumbnails/thumbnail_tab_helper.cc

 // Copyright (c) 2012 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/thumbnails/thumbnail_tab_helper.h"
 
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/thumbnails/thumbnail_service.h"
 #include "chrome/browser/thumbnails/thumbnail_service_factory.h"
@@ skipping 100 matching lines @@
   copy_rect.Inset(0, 0, scrollbar_size, scrollbar_size);
 
   if (copy_rect.IsEmpty())
     return;
 
   context->clip_result = algorithm->GetCanvasCopyInfo(
       copy_rect.size(),
       ui::GetScaleFactorForNativeView(view->GetNativeView()),
       &copy_rect,
       &context->requested_copy_size);
-
+  SkBitmap::Config preferred_format =
+      render_widget_host->PreferredReadbackFormat();
   render_widget_host->CopyFromBackingStore(
       copy_rect,
       context->requested_copy_size,
-      base::Bind(&ProcessCapturedBitmap, context, algorithm));
+      base::Bind(&ProcessCapturedBitmap, context, algorithm),
+      preferred_format);

[piman, 2014/03/10 18:27:20]

I believe the receiving path expects 8888 bitmaps.

[sivag, 2014/03/11 14:41:50]

Done.

 }
 
 }  // namespace
 
 ThumbnailTabHelper::ThumbnailTabHelper(content::WebContents* contents)
     : content::WebContentsObserver(contents),
       enabled_(true),
       load_interrupted_(false) {
   // Even though we deal in RenderWidgetHosts, we only care about its
   // subclass, RenderViewHost when it is in a tab. We don't make thumbnails
@@ skipping 97 matching lines @@
         content::NOTIFICATION_RENDER_WIDGET_VISIBILITY_CHANGED,
         content::Source<RenderWidgetHost>(renderer));
   }
 }
 
 void ThumbnailTabHelper::WidgetHidden(RenderWidgetHost* widget) {
   if (!enabled_)
     return;
   UpdateThumbnailIfNecessary(web_contents());
 }