Fix issue with drawColor(color, Mode.Clear)

Change-Id: I486b24a5b609c6f8adb0276037ddb24af2b888b2
diff --git a/libs/hwui/OpenGLRenderer.h b/libs/hwui/OpenGLRenderer.h
index 70abe88..e2dbba0 100644
--- a/libs/hwui/OpenGLRenderer.h
+++ b/libs/hwui/OpenGLRenderer.h
@@ -478,6 +478,7 @@
     void setupDrawAALine(GLvoid* vertices, GLvoid* distanceCoords, GLvoid* lengthCoords,
             float strokeWidth);
     void finishDrawTexture();
+    void accountForClear(SkXfermode::Mode mode);
 
     void drawRegionRects(const Region& region);