Remove canTweakAlphaForCoverage from XP's since batch reads flag.

src/gpu/GrPipelineBuilder.h

Index: src/gpu/GrPipelineBuilder.h
diff --git a/src/gpu/GrPipelineBuilder.h b/src/gpu/GrPipelineBuilder.h
index 24d72e80aa04e419124839c3f4a3c2e0435f4ef4..fa085f0b993153bec51753f3edab933a3c4b6155 100644
--- a/src/gpu/GrPipelineBuilder.h
+++ b/src/gpu/GrPipelineBuilder.h
@@ -139,13 +139,6 @@ public:
     ////
 
     /**
-     * Determines whether multiplying the computed per-pixel color by the pixel's fractional
-     * coverage before the blend will give the correct final destination color. In general it
-     * will not as coverage is applied after blending.
-     */
-    bool canTweakAlphaForCoverage() const;
-
-    /**
      * This function returns true if the render target destination pixel values will be read for
      * blending during draw.
      */