rename getBitmapDC to beginPlatformPaint and add calls to endPlatformPaint

skia/ext/platform_canvas_linux.cc

-// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
+// 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 "skia/ext/platform_canvas.h"
 
 #include <cairo/cairo.h>
 
 #include "skia/ext/platform_device_linux.h"
 #include "skia/ext/bitmap_platform_device_linux.h"
 #include "third_party/skia/include/core/SkTypes.h"
@@ skipping 14 matching lines @@
 }
 
 PlatformCanvas::~PlatformCanvas() {
 }
 bool PlatformCanvas::initialize(int width, int height, bool is_opaque,
                                 uint8_t* data) {
   return initializeWithDevice(BitmapPlatformDevice::Create(
       width, height, is_opaque, data));
 }
 
-cairo_t* PlatformCanvas::beginPlatformPaint() {
+cairo_t* PlatformCanvas::beginPlatformPaint() const {
   return getTopPlatformDevice().beginPlatformPaint();
 }
 
-void PlatformCanvas::endPlatformPaint() {
+void PlatformCanvas::endPlatformPaint() const {
   // We don't need to do anything on Linux here.
 }
 
 }  // namespace skia