Remove canApplyCoverage from XP and all related functions in gpu code.

include/gpu/GrXferProcessor.h

Index: include/gpu/GrXferProcessor.h
diff --git a/include/gpu/GrXferProcessor.h b/include/gpu/GrXferProcessor.h
index 301390db7314498094feb3d8d57902fe7e1345e2..a79e6cd197a800415ab9b638ea3878301b3a05f2 100644
--- a/include/gpu/GrXferProcessor.h
+++ b/include/gpu/GrXferProcessor.h
@@ -200,18 +200,6 @@ public:
      */
     virtual bool supportsRGBCoverage(GrColor knownColor, uint32_t knownColorFlags) const = 0;
 
-    /**
-     * Depending on color blend mode requested it may or may not be possible to correctly blend with
-     * fractional pixel coverage generated by the fragment shader.
-     *
-     * This function considers the known color and coverage input into the xfer processor and
-     * certain state information (colorWriteDisabled) to determine whether
-     * coverage can be handled correctly.
-     */
-    virtual bool canApplyCoverage(const GrProcOptInfo& colorPOI,
-                                  const GrProcOptInfo& coveragePOI) const = 0;
-
-
     struct InvariantOutput {
         bool        fWillBlendWithDst;
         GrColor     fBlendedColor;