Optionally clear PlatformCanvas instances.

ui/gfx/canvas_skia.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 "ui/gfx/canvas_skia.h"
 
 #include <limits>
 
 #include "base/i18n/rtl.h"
 #include "base/logging.h"
@@ skipping 35 matching lines @@
 
 namespace gfx {
 
 ////////////////////////////////////////////////////////////////////////////////
 // CanvasSkia, public:
 
 CanvasSkia::CanvasSkia(const gfx::Size& size, bool is_opaque)
     : owned_canvas_(new skia::PlatformCanvas(size.width(), size.height(),
                                              is_opaque)),
       canvas_(owned_canvas_.get()) {
+#if defined(OS_WIN) || defined(OS_MACOSX)
+  owned_canvas_->drawARGB(0, 0, 0, 0);
+#endif
 }
 
 CanvasSkia::CanvasSkia(const SkBitmap& bitmap, bool is_opaque)
     : owned_canvas_(new skia::PlatformCanvas(bitmap.width(), bitmap.height(),
                                              is_opaque)),
       canvas_(owned_canvas_.get()) {
   DrawBitmapInt(bitmap, 0, 0);
 }
 
 CanvasSkia::CanvasSkia()
@@ skipping 361 matching lines @@
 
 CanvasPaint* CanvasPaint::CreateCanvasPaint(gfx::NativeView view) {
 #if defined(OS_WIN) && !defined(USE_AURA)
   return new CanvasPaintWin(view);
 #else
   return NULL;
 #endif
 }
 
 }  // namespace gfx