guard to remove DrawBitmapRectFlags

BUG=skia:

Review URL: https://codereview.chromium.org/1235393003
diff --git a/samplecode/SampleApp.cpp b/samplecode/SampleApp.cpp
index a80ccd9..508ff63 100644
--- a/samplecode/SampleApp.cpp
+++ b/samplecode/SampleApp.cpp
@@ -1116,7 +1116,7 @@
         // Clear the background behind our zoomed in view
         paint.setColor(SK_ColorWHITE);
         canvas->drawRect(dest, paint);
-        canvas->drawBitmapRect(bitmap, &src, dest);
+        canvas->drawBitmapRect(bitmap, src, dest, NULL);
         paint.setColor(SK_ColorBLACK);
         paint.setStyle(SkPaint::kStroke_Style);
         // Draw a border around the pixel in the middle