Revert "switch GatherPixelRefs to use SkBaseDevice instead of SkBitmapDevice"

include/core/SkBitmapDevice.h

Index: include/core/SkBitmapDevice.h
diff --git a/include/core/SkBitmapDevice.h b/include/core/SkBitmapDevice.h
index b5265267e695adc042a95bf82fb5edfe9bfb8710..530b85c9f8199753db290498cdc90ff3e909eea9 100644
--- a/include/core/SkBitmapDevice.h
+++ b/include/core/SkBitmapDevice.h
@@ -73,6 +73,13 @@ public:
     */
     virtual int height() const SK_OVERRIDE { return fBitmap.height(); }
 
+    /**
+     *  Return the bounds of the device in the coordinate space of the root
+     *  canvas. The root device will have its top-left at 0,0, but other devices
+     *  such as those associated with saveLayer may have a non-zero origin.
+     */
+    virtual void getGlobalBounds(SkIRect* bounds) const SK_OVERRIDE;
+
     /** Returns true if the device's bitmap's config treats every pixels as
         implicitly opaque.
     */