implement isABitmap for imageshader, return localmatrix for bitmap's impl

src/image/SkImageShader.h

Index: src/image/SkImageShader.h
diff --git a/src/image/SkImageShader.h b/src/image/SkImageShader.h
index 10200e97d5b10ec12ffba4315b7ccd3a47a8ae87..160de7ac9c4b7d38df4c03f613884cb82c01d623 100644
--- a/src/image/SkImageShader.h
+++ b/src/image/SkImageShader.h
@@ -29,6 +29,8 @@ protected:
     void flatten(SkWriteBuffer&) const override;
     size_t onContextSize(const ContextRec&) const override;
     Context* onCreateContext(const ContextRec&, void* storage) const override;
+    bool onIsABitmap(SkBitmap*, SkMatrix*, TileMode*) const override;
+    SkImage* onIsAImage(SkMatrix*, TileMode*) const override;
 
     SkAutoTUnref<const SkImage> fImage;
     const TileMode              fTileModeX;