Remove willReadDst from GrFragmentProcessor.

Since only XP's can read dst now, there is no reason to have this query on GrFP.
This also triggered a chain reaction of cleaning up/removing unnecessary code
elsewhere.

BUG=skia:

Review URL: https://codereview.chromium.org/851143003

1 files changed, 1 insertions, 4 deletions

diff --git a/src/effects/SkArithmeticMode_gpu.h b/src/effects/SkArithmeticMode_gpu.h
index 424bef6f91..2998eabc3b 100644
--- a/src/effects/SkArithmeticMode_gpu.h
+++ b/src/effects/SkArithmeticMode_gpu.h
@@ -154,10 +154,7 @@ public:
     void getInvariantOutput(const GrProcOptInfo& colorPOI, const GrProcOptInfo& coveragePOI,
                             GrXPFactory::InvariantOutput*) const SK_OVERRIDE;
 
-    bool willReadDst(const GrProcOptInfo& colorPOI,
-                     const GrProcOptInfo& coveragePOI) const SK_OVERRIDE {
-        return true;
-    }
+    bool willReadDst() const SK_OVERRIDE { return true; }
 
 private:
     GrArithmeticXPFactory(float k1, float k2, float k3, float k4, bool enforcePMColor);