guard to remove DrawBitmapRectFlags

BUG=skia:

Review URL: https://codereview.chromium.org/1235393003
diff --git a/src/utils/debugger/SkDrawCommand.cpp b/src/utils/debugger/SkDrawCommand.cpp
index 5f0f74f..1d28d2e 100644
--- a/src/utils/debugger/SkDrawCommand.cpp
+++ b/src/utils/debugger/SkDrawCommand.cpp
@@ -129,7 +129,7 @@
                                   yScale * input.height());
 
     canvas->clear(0xFFFFFFFF);
-    canvas->drawBitmapRect(input, NULL, dst);
+    canvas->drawBitmapRect(input, dst);
 
     if (srcRect) {
         SkRect r = SkRect::MakeLTRB(srcRect->fLeft * xScale + SK_Scalar1,