Add override to force bitmap rendering

R=robertphillips@google.com

Author: krajcevski@google.com

Review URL: https://codereview.chromium.org/462203002
diff --git a/src/gpu/GrClipMaskManager.cpp b/src/gpu/GrClipMaskManager.cpp
index 0f79402..7cafdf7 100644
--- a/src/gpu/GrClipMaskManager.cpp
+++ b/src/gpu/GrClipMaskManager.cpp
@@ -1058,7 +1058,7 @@
     SkMatrix matrix;
     matrix.setTranslate(SkIntToScalar(-clipSpaceIBounds.fLeft),
                         SkIntToScalar(-clipSpaceIBounds.fTop));
-    helper.init(maskSpaceIBounds, &matrix);
+    helper.init(maskSpaceIBounds, &matrix, false);
 
     helper.clear(kAllIn_InitialState == initialState ? 0xFF : 0x00);