Working patch to remove constant attributes.  This may cause some gm mismatches, I will rebaseline tonight.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/84c94c0dfd1e12e97d8a835882dda575f36e41d2

Review URL: https://codereview.chromium.org/678073005
diff --git a/src/gpu/effects/GrYUVtoRGBEffect.cpp b/src/gpu/effects/GrYUVtoRGBEffect.cpp
index f02c1b2..703c672 100644
--- a/src/gpu/effects/GrYUVtoRGBEffect.cpp
+++ b/src/gpu/effects/GrYUVtoRGBEffect.cpp
@@ -109,7 +109,7 @@
     virtual void onComputeInvariantOutput(InvariantOutput* inout) const SK_OVERRIDE {
         // YUV is opaque
         inout->setToOther(kA_GrColorComponentFlag, 0xFF << GrColor_SHIFT_A,
-                          InvariantOutput::kWill_ReadInput);
+                          InvariantOutput::kWillNot_ReadInput);
     }
 
     GrCoordTransform fCoordTransform;