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

src/gpu/GrPipelineBuilder.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 GrPipelineBuilder_DEFINED
 #define GrPipelineBuilder_DEFINED
 
@@ skipping 257 matching lines @@
     /// @}
 
     ///////////////////////////////////////////////////////////////////////////
     /// @name State Flags
     ////
 
     /**
      *  Flags that affect rendering. Controlled using enable/disableState(). All
      *  default to disabled.
      */
-    enum StateBits {
+    enum Flags {
         /**
          * Perform dithering. TODO: Re-evaluate whether we need this bit
          */
-        kDither_StateBit        = 0x01,
+        kDither_Flag        = 0x01,
         /**
          * Perform HW anti-aliasing. This means either HW FSAA, if supported by the render target,
          * or smooth-line rendering if a line primitive is drawn and line smoothing is supported by
          * the 3D API.
          */
-        kHWAntialias_StateBit   = 0x02,
+        kHWAntialias_Flag   = 0x02,
 
-        kLast_StateBit = kHWAntialias_StateBit,
+        /**
+         * Modifies the vertex shader so that vertices will be positioned at pixel centers.
+         */
+        kSnapVerticesToPixelCenters_Flag = 0x04,
+
+        kLast_Flag = kSnapVerticesToPixelCenters_Flag,
     };
 
-    bool isDither() const { return 0 != (fFlagBits & kDither_StateBit); }
-    bool isHWAntialias() const { return 0 != (fFlagBits & kHWAntialias_StateBit); }
+    bool isDither() const { return SkToBool(fFlags & kDither_Flag); }
+    bool isHWAntialias() const { return SkToBool(fFlags & kHWAntialias_Flag); }
+    bool snapVerticesToPixelCenters() const {
+        return SkToBool(fFlags & kSnapVerticesToPixelCenters_Flag); }
 
     /**
      * Enable render state settings.
      *
-     * @param stateBits bitfield of StateBits specifying the states to enable
+     * @param flags bitfield of Flags specifying the states to enable
      */
-    void enableState(uint32_t stateBits) { fFlagBits |= stateBits; }
-
+    void enableState(uint32_t flags) { fFlags |= flags; }
+        
     /**
      * Disable render state settings.
      *
-     * @param stateBits bitfield of StateBits specifying the states to disable
+     * @param flags bitfield of Flags specifying the states to disable
      */
-    void disableState(uint32_t stateBits) { fFlagBits &= ~(stateBits); }
+    void disableState(uint32_t flags) { fFlags &= ~(flags); }
 
     /**
-     * Enable or disable stateBits based on a boolean.
+     * Enable or disable flags based on a boolean.
      *
-     * @param stateBits bitfield of StateBits to enable or disable
+     * @param flags bitfield of Flags to enable or disable
      * @param enable    if true enable stateBits, otherwise disable
      */
-    void setState(uint32_t stateBits, bool enable) {
+    void setState(uint32_t flags, bool enable) {
         if (enable) {
-            this->enableState(stateBits);
+            this->enableState(flags);
         } else {
-            this->disableState(stateBits);
+            this->disableState(flags);
         }
     }
 
     /// @}
 
     ///////////////////////////////////////////////////////////////////////////
     /// @name Face Culling
     ////
 
     enum DrawFace {
@@ skipping 84 matching lines @@
      */
     void calcCoverageInvariantOutput(GrColor) const;
 
     // Some of the auto restore objects assume that no effects are removed during their lifetime.
     // This is used to assert that this condition holds.
     SkDEBUGCODE(int fBlockEffectRemovalCnt;)
 
     typedef SkSTArray<4, GrFragmentStage> FragmentStageArray;
 
     SkAutoTUnref<GrRenderTarget>            fRenderTarget;
-    uint32_t                                fFlagBits;
+    uint32_t                                fFlags;
     GrStencilSettings                       fStencilSettings;
     DrawFace                                fDrawFace;
     mutable SkAutoTUnref<const GrXPFactory> fXPFactory;
     FragmentStageArray                      fColorStages;
     FragmentStageArray                      fCoverageStages;
     GrClip                                  fClip;
 
     mutable GrProcOptInfo fColorProcInfo;
     mutable GrProcOptInfo fCoverageProcInfo;
     mutable bool fColorProcInfoValid;
     mutable bool fCoverageProcInfoValid;
     mutable GrColor fColorCache;
     mutable GrColor fCoverageCache;
 
     friend class GrPipeline;
 };
 
 #endif