Implement srcRect and dstRect functionality in SkBitmapSource. This is required for the "preserveAs…

gm/tileimagefilter.cpp

Index: gm/tileimagefilter.cpp
diff --git a/gm/tileimagefilter.cpp b/gm/tileimagefilter.cpp
index 9a14344772e2b60687f73ea865e442986e188bf5..48d65ca0730b904f404dec533979367c62b14035 100644
--- a/gm/tileimagefilter.cpp
+++ b/gm/tileimagefilter.cpp
@@ -70,9 +70,10 @@ protected:
     void drawClippedBitmap(SkCanvas* canvas, const SkBitmap& bitmap, const SkPaint& paint,
                            SkScalar x, SkScalar y) {
         canvas->save();
-        canvas->clipRect(SkRect::MakeXYWH(x, y,
+        canvas->translate(x, y);
+        canvas->clipRect(SkRect::MakeXYWH(0, 0,
             SkIntToScalar(bitmap.width()), SkIntToScalar(bitmap.height())));
-        canvas->drawBitmap(bitmap, x, y, &paint);
+        canvas->drawBitmap(bitmap, 0, 0, &paint);
         canvas->restore();
     }