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

src/gpu/GrProgramDesc.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrProgramDesc_DEFINED
 #define GrProgramDesc_DEFINED
 
@@ skipping 38 matching lines @@
     }
 
     static bool Less(const GrProgramDesc& a, const GrProgramDesc& b) {
         return memcmp(a.asKey(), b.asKey(), a.keyLength() & ~0x3) < 0;
     }
 
     struct KeyHeader {
         uint8_t                     fFragPosKey;   // set by GrGLShaderBuilder if there are
                                                    // effects that read the fragment position.
                                                    // Otherwise, 0.
-
+        uint8_t                     fSnapVerticesToPixelCenters;
         int8_t                      fColorEffectCnt;
         int8_t                      fCoverageEffectCnt;
     };
+    GR_STATIC_ASSERT(sizeof(KeyHeader) == 4);
 
     int numColorEffects() const {
         return this->header().fColorEffectCnt;
     }
 
     int numCoverageEffects() const {
         return this->header().fCoverageEffectCnt;
     }
 
     int numTotalEffects() const { return this->numColorEffects() + this->numCoverageEffects(); }
@@ skipping 43 matching lines @@
     };
 
     SkSTArray<kPreAllocSize, uint8_t, true>& key() { return fKey; }
     const SkSTArray<kPreAllocSize, uint8_t, true>& key() const { return fKey; }
 
 private:
     SkSTArray<kPreAllocSize, uint8_t, true> fKey;
 };
 
 #endif