Use texture barriers to read directly from the RT

src/gpu/GrPipelineBuilder.cpp

Index: src/gpu/GrPipelineBuilder.cpp
diff --git a/src/gpu/GrPipelineBuilder.cpp b/src/gpu/GrPipelineBuilder.cpp
index 1d8aa4f2b4f9baa9b21496272dfac6b7f04c85f7..5e740ecb40408e7c659a3cdc0a3204b77f0ccda7 100644
--- a/src/gpu/GrPipelineBuilder.cpp
+++ b/src/gpu/GrPipelineBuilder.cpp
@@ -123,6 +123,11 @@ bool GrPipelineBuilder::canTweakAlphaForCoverage() const {
     return this->getXPFactory()->canTweakAlphaForCoverage();
 }
 
+// Some blending extensions require the use of a barrier to ensure coherent results.
+bool GrPipelineBuilder::willBlendCoherently(const GrDrawTargetCaps& caps) const {
+    return this->getXPFactory()->willBlendCoherently(caps);

[Mark Kilgard, 2015/04/02 23:02:38]

this seems a lot of indirection to just return a boolean that hopefully will be
false most of the time

could the knowledge be cached within the GrPipelineBuilder?

+}
+
 ////////////////////////////////////////////////////////////////////////////////
 
 GrPipelineBuilder::~GrPipelineBuilder() {