Update use of SkCanvas and SkDevice to match change in Skia

skia/ext/platform_canvas.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 "skia/ext/platform_canvas.h"
+
+#include "skia/ext/bitmap_platform_device.h"
 #include "third_party/skia/include/core/SkTypes.h"
 
 namespace skia {
 
+PlatformCanvas::PlatformCanvas()
+    : SkCanvas(SkNEW(SkBitmapPlatformDeviceFactory)) {
+}
+
+PlatformCanvas::PlatformCanvas(SkDeviceFactory* factory) : SkCanvas(factory) {
+}
+
 SkDevice* PlatformCanvas::setBitmapDevice(const SkBitmap&) {
   SkASSERT(false);  // Should not be called.
   return NULL;
 }
 
 PlatformDevice& PlatformCanvas::getTopPlatformDevice() const {
   // All of our devices should be our special PlatformDevice.
   SkCanvas::LayerIter iter(const_cast<PlatformCanvas*>(this), false);
   return *static_cast<PlatformDevice*>(iter.device());
 }
 
 // static
 size_t PlatformCanvas::StrideForWidth(unsigned width) {
   return 4 * width;
 }
 
 }  // namespace skia