Refactor the platform canvas unit test a bit so that it can be run on...

base/gfx/platform_canvas_mac.cc

 // Copyright (c) 2006-2008 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 "base/gfx/platform_canvas_mac.h"
 
 #include "base/gfx/bitmap_platform_device_mac.h"
 #include "base/logging.h"
 
 namespace gfx {
@@ skipping 123 matching lines @@
 
 SkDevice* PlatformCanvasMac::createPlatformDevice(int width,
                                                int height,
                                                bool is_opaque,
                                                CGContextRef context) {
   SkDevice* device = BitmapPlatformDeviceMac::Create(context, width, height,
                                                   is_opaque);
   return device;
 }
 
+SkDevice* PlatformCanvasMac::setBitmapDevice(const SkBitmap&) {
+  NOTREACHED();
+  return NULL;
+}
+
 }  // namespace gfx