Fleshed out GPU portion of image/surface feature

https://codereview.appspot.com/6813055/



git-svn-id: http://skia.googlecode.com/svn/trunk@6214 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/image/SkSurface_Picture.cpp b/src/image/SkSurface_Picture.cpp
index bac09c5..3f82634 100644
--- a/src/image/SkSurface_Picture.cpp
+++ b/src/image/SkSurface_Picture.cpp
@@ -24,6 +24,7 @@
     virtual SkImage* onNewImageShapshot() SK_OVERRIDE;
     virtual void onDraw(SkCanvas*, SkScalar x, SkScalar y,
                         const SkPaint*) SK_OVERRIDE;
+    virtual void onCopyOnWrite(SkImage*, SkCanvas*) SK_OVERRIDE;
 
 private:
     SkPicture*  fPicture;
@@ -75,6 +76,11 @@
     SkImagePrivDrawPicture(canvas, fPicture, x, y, paint);
 }
 
+void SkSurface_Picture::onCopyOnWrite(SkImage* cachedImage, SkCanvas*) {
+    // We always spawn a copy of the recording picture when we 
+    // are asked for a snapshot, so we never need to do anything here.
+}
+
 ///////////////////////////////////////////////////////////////////////////////