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

skia/ext/platform_canvas_mac.cc

Index: skia/ext/platform_canvas_mac.cc
diff --git a/skia/ext/platform_canvas_mac.cc b/skia/ext/platform_canvas_mac.cc
index 7e4c6108ccf4204b1a57f91b69aff3736e24da9e..dd893947bb278e65f25397f2ee8f6d760c302ac6 100644
--- a/skia/ext/platform_canvas_mac.cc
+++ b/skia/ext/platform_canvas_mac.cc
@@ -19,7 +19,7 @@ PlatformCanvas::PlatformCanvas(int width,
                                bool is_opaque,
                                CGContextRef context)
     : SkCanvas(SkNEW(BitmapPlatformDeviceFactory)) {
-  initialize(width, height, is_opaque);
+  initialize(context, width, height, is_opaque);
 }
 
 PlatformCanvas::PlatformCanvas(int width,
@@ -37,8 +37,19 @@ bool PlatformCanvas::initialize(int width,
                                 int height,
                                 bool is_opaque,
                                 uint8_t* data) {
-  SkDevice* device = BitmapPlatformDevice::CreateWithData(data, width, height,
-                                                          is_opaque);
+  return initialize(BitmapPlatformDevice::CreateWithData(data, width, height,
+                                                         is_opaque));
+}
+
+bool PlatformCanvas::initialize(CGContextRef context,
+                                int width,
+                                int height,
+                                bool is_opaque) {
+  return initialize(BitmapPlatformDevice::Create(context, width, height,
+                                                 is_opaque));
+}
+
+bool PlatformCanvas::initialize(SkDevice* device) {
   if (!device)
     return false;