Update use of SkCanvas and SkDevice to match change in Skia

skia/ext/platform_canvas.cc

Index: skia/ext/platform_canvas.cc
diff --git a/skia/ext/platform_canvas.cc b/skia/ext/platform_canvas.cc
index 9121a0db0591a32d61c2b4cd06b7a0c1803effed..de0ed13d65a70c4ebcf0786227910ff1bfbccb55 100644
--- a/skia/ext/platform_canvas.cc
+++ b/skia/ext/platform_canvas.cc
@@ -3,10 +3,19 @@
 // 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;