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

src/gpu/GrPipeline.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrPipeline_DEFINED
 #define GrPipeline_DEFINED
 
@@ skipping 62 matching lines @@
      * @return    The currently set render target.
      */
     GrRenderTarget* getRenderTarget() const { return fRenderTarget.get(); }
 
     const GrStencilSettings& getStencil() const { return fStencilSettings; }
 
     const GrScissorState& getScissorState() const { return fScissorState; }
 
     bool isDitherState() const { return SkToBool(fFlags & kDither_Flag); }
     bool isHWAntialiasState() const { return SkToBool(fFlags & kHWAA_Flag); }
+    bool snapVerticesToPixelCenters() const { return SkToBool(fFlags & kSnapVertices_Flag); }
     // Skip any draws that refer to this pipeline (they should be a no-op).
     bool mustSkip() const { return NULL == this->getRenderTarget(); }
 
     /**
      * Gets whether the target is drawing clockwise, counterclockwise,
      * or both faces.
      * @return the current draw face(s).
      */
     GrPipelineBuilder::DrawFace getDrawFace() const { return fDrawFace; }
 
@@ skipping 19 matching lines @@
      * Calculates the primary and secondary output types of the shader. For certain output types
      * the function may adjust the blend coefficients. After this function is called the src and dst
      * blend coeffs will represent those used by backend API.
      */
     void setOutputStateInfo(const GrPipelineBuilder& ds, GrXferProcessor::OptFlags,
                             const GrDrawTargetCaps&);
 
     enum Flags {
         kDither_Flag            = 0x1,
         kHWAA_Flag              = 0x2,
+        kSnapVertices_Flag      = 0x4,
     };
 
     typedef GrPendingIOResource<GrRenderTarget, kWrite_GrIOType> RenderTarget;
     typedef SkSTArray<8, GrPendingFragmentStage> FragmentStageArray;
     typedef GrPendingProgramElement<const GrXferProcessor> ProgramXferProcessor;
     RenderTarget                        fRenderTarget;
     GrScissorState                      fScissorState;
     GrStencilSettings                   fStencilSettings;
     GrPipelineBuilder::DrawFace         fDrawFace;
     uint32_t                            fFlags;
     ProgramXferProcessor                fXferProcessor;
     FragmentStageArray                  fFragmentStages;
     bool                                fReadsFragPosition;
     GrPipelineInfo                      fInitBT;
 
     // This function is equivalent to the offset into fFragmentStages where coverage stages begin.
     int                                 fNumColorStages;
 
     GrProgramDesc fDesc;
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif