Make non-AA hairline stroke rects snap to pixels centers so they close.

src/gpu/GrPipeline.cpp

Index: src/gpu/GrPipeline.cpp
diff --git a/src/gpu/GrPipeline.cpp b/src/gpu/GrPipeline.cpp
index fc9f4eab12ecb1b4171bed990eca4f73841f0f10..8074addb2c93977bd9711626645b970ecd2f78c5 100644
--- a/src/gpu/GrPipeline.cpp
+++ b/src/gpu/GrPipeline.cpp
@@ -64,6 +64,9 @@ GrPipeline::GrPipeline(const GrPipelineBuilder& pipelineBuilder,
     if (pipelineBuilder.isDither()) {
         fFlags |= kDither_Flag;
     }
+    if (pipelineBuilder.snapVerticesToPixelCenters()) {
+        fFlags |= kSnapVertices_Flag;
+    }
 
     int firstColorStageIdx = colorPOI.firstEffectiveStageIndex();