Add isUnblended query to GrDrawState.

src/gpu/GrDrawState.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrDrawState.h"
 
 #include "GrOptDrawState.h"
@@ skipping 724 matching lines @@
         }
 
         // Since the shader will multiply coverage and color, the only way the final A==1 is if
         // coverage and color both have A==1.
         return (inoutColor.isOpaque() && inoutCoverage.isOpaque());
     }
 
     return inoutColor.isOpaque();
 }
 
+bool GrDrawState::willBlendWithDst() const {
+    if (!this->hasSolidCoverage()) {
+        return true;
+    }
+
+    bool srcAIsOne = this->srcAlphaWillBeOne();
+    GrBlendCoeff srcCoeff = this->getSrcBlendCoeff();
+    GrBlendCoeff dstCoeff = this->getDstBlendCoeff();
+    if (kISA_GrBlendCoeff == dstCoeff && srcAIsOne) {
+        dstCoeff = kZero_GrBlendCoeff;
+    }
+    if (kOne_GrBlendCoeff != srcCoeff ||
+        kZero_GrBlendCoeff != dstCoeff ||
+        this->willEffectReadDstColor()) {
+        return true;
+    }
+
+    return false;
+}
+