Optionally clear PlatformCanvas instances.

content/browser/renderer_host/backing_store_win.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_win.h"
 
 #include "base/command_line.h"
 #include "content/browser/renderer_host/render_process_host_impl.h"
 #include "content/browser/renderer_host/render_widget_host.h"
 #include "content/public/common/content_switches.h"
@@ skipping 140 matching lines @@
                       paint_rect.y() - bitmap_rect.y(),
                       paint_rect.width(),
                       paint_rect.height(),
                       dib->memory(),
                       reinterpret_cast<BITMAPINFO*>(&hdr));
   }
 }
 
 bool BackingStoreWin::CopyFromBackingStore(const gfx::Rect& rect,
                                            skia::PlatformCanvas* output) {
-  if (!output->initialize(rect.width(), rect.height(), true))
+  if (!output->initialize(rect.width(), rect.height(),
+                          skia::PlatformDevice::FLAGS_OPAQUE))
     return false;
 
   skia::ScopedPlatformPaint scoped_platform_paint(output);
   HDC temp_dc = scoped_platform_paint.GetPlatformSurface();
   BitBlt(temp_dc, 0, 0, rect.width(), rect.height(),
          hdc(), rect.x(), rect.y(), SRCCOPY);
   return true;
 }
 
 void BackingStoreWin::ScrollBackingStore(int dx, int dy,
                                          const gfx::Rect& clip_rect,
                                          const gfx::Size& view_size) {
   RECT damaged_rect, r = clip_rect.ToRECT();
   ScrollDC(hdc_, dx, dy, NULL, &r, NULL, &damaged_rect);
 
   // TODO(darin): this doesn't work if dx and dy are both non-zero!
   DCHECK(dx == 0 || dy == 0);
 }