Relax constraints on src coeff in GrDrawState::willBlendWithDst.

src/gpu/GrDrawState.cpp

Index: src/gpu/GrDrawState.cpp
diff --git a/src/gpu/GrDrawState.cpp b/src/gpu/GrDrawState.cpp
index 23ebea6afcfd9cbbb4f476edea789b46e21118d4..4ae93bfaf0ad8220a4a6462bc6ec422ba9f14a71 100644
--- a/src/gpu/GrDrawState.cpp
+++ b/src/gpu/GrDrawState.cpp
@@ -7,6 +7,7 @@
 
 #include "GrDrawState.h"
 
+#include "GrBlend.h"
 #include "GrInvariantOutput.h"
 #include "GrOptDrawState.h"
 #include "GrPaint.h"
@@ -755,7 +756,7 @@ bool GrDrawState::willBlendWithDst() const {
     if (kISA_GrBlendCoeff == dstCoeff && srcAIsOne) {

[bsalomon, 2014/11/12 21:33:38]

At a minimum we can just change this srcAIsOne to this->srcAlphaWillBeOne() and
remove the above line so that it isn't called unless dstCoeff is kISA.

Otherwise, lgtm.

         dstCoeff = kZero_GrBlendCoeff;
     }
-    if (kOne_GrBlendCoeff != srcCoeff ||
+    if (GrBlendCoeffRefsDst(srcCoeff) ||
         kZero_GrBlendCoeff != dstCoeff ||
         this->willEffectReadDstColor()) {
         return true;