Allow the creation of a skia::PlatformCanvas from a CGContextRef.

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 {
@@ skipping 14 matching lines @@
   // 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;
 }
 
+bool PlatformCanvas::initializeWithDevice(SkDevice* device) {
+  if (!device)
+    return false;
+
+  setDevice(device);
+  device->unref();  // Was created with refcount 1, and setDevice also refs.
+  return true;
+}
+
 }  // namespace skia