Optionally clear PlatformCanvas instances.

content/browser/renderer_host/backing_store_skia.cc

 // Copyright (c) 2011 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 "content/browser/renderer_host/backing_store_skia.h"
 
 #include "content/browser/renderer_host/render_process_host_impl.h"
 #include "skia/ext/platform_canvas.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "ui/gfx/canvas.h"
@@ skipping 80 matching lines @@
   int w = clip_rect.width() + abs(dx);
   int h = clip_rect.height() + abs(dy);
   SkIRect rect = SkIRect::MakeXYWH(x, y, w, h);
   bitmap_.scrollRect(&rect, dx, dy);
 }
 
 bool BackingStoreSkia::CopyFromBackingStore(const gfx::Rect& rect,
                                             skia::PlatformCanvas* output) {
   const int width = std::min(size().width(), rect.width());
   const int height = std::min(size().height(), rect.height());
-  if (!output->initialize(width, height, true))
+  if (!output->initialize(width, height, skia::PlatformDevice::FLAGS_OPAQUE))
     return false;
 
   SkBitmap bitmap = skia::GetTopDevice(*output)->accessBitmap(true);
   SkIRect skrect = SkIRect::MakeXYWH(rect.x(), rect.y(), width, height);
   SkBitmap b;
   if (!canvas_->readPixels(skrect, &b))
     return false;
   output->writePixels(b, rect.x(), rect.y());
   return true;
 }