Move willColorBlendWithDst from pipeline builder to GrPipelineOptimizations.

Review URL: https://codereview.chromium.org/1285193004
diff --git a/src/gpu/GrPipeline.cpp b/src/gpu/GrPipeline.cpp
index a2b6d7f..8f149f5 100644
--- a/src/gpu/GrPipeline.cpp
+++ b/src/gpu/GrPipeline.cpp
@@ -120,6 +120,13 @@
     if (SkToBool(optFlags & GrXferProcessor::kCanTweakAlphaForCoverage_OptFlag)) {
         opts->fFlags |= GrPipelineOptimizations::kCanTweakAlphaForCoverage_Flag; 
     }
+
+    GrXPFactory::InvariantBlendedColor blendedColor;
+    builder.fXPFactory->getInvariantBlendedColor(args.fColorPOI, &blendedColor);
+    if (blendedColor.fWillBlendWithDst) {
+        opts->fFlags |= GrPipelineOptimizations::kWillColorBlendWithDst_Flag;
+    }
+
     return pipeline;
 }