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

BUG=skia:3717

Review URL: https://codereview.chromium.org/1101663007
diff --git a/src/gpu/gl/GrGLProgramDesc.cpp b/src/gpu/gl/GrGLProgramDesc.cpp
index 96a8ada..87e7f2d 100644
--- a/src/gpu/gl/GrGLProgramDesc.cpp
+++ b/src/gpu/gl/GrGLProgramDesc.cpp
@@ -143,7 +143,7 @@
     } else {
         header->fFragPosKey = 0;
     }
-
+    header->fSnapVerticesToPixelCenters = pipeline.snapVerticesToPixelCenters();
     header->fColorEffectCnt = pipeline.numColorFragmentStages();
     header->fCoverageEffectCnt = pipeline.numCoverageFragmentStages();
     glDesc->finalize();