Add isUnblended query to GrDrawState.

src/gpu/GrDrawState.cpp

Index: src/gpu/GrDrawState.cpp
diff --git a/src/gpu/GrDrawState.cpp b/src/gpu/GrDrawState.cpp
index c82c5adad1f771354e711e1ce149234d8ee77acf..4341d00ccedc367381341d795e0a73b7b07776b2 100644
--- a/src/gpu/GrDrawState.cpp
+++ b/src/gpu/GrDrawState.cpp
@@ -742,3 +742,23 @@ bool GrDrawState::srcAlphaWillBeOne() const {
     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;
+}
+