fix for chrome bug with sub pixel hairlines

src/gpu/gl/builders/GrGLProgramBuilder.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrGLProgramBuilder.h"
 #include "gl/GrGLProgram.h"
 #include "gl/GrGLSLPrettyPrint.h"
@@ skipping 219 matching lines @@
         GrGLSLExpr4 outputColor;
         GrGLSLExpr4 outputCoverage;
         this->emitAndInstallProc(gp, &outputColor, &outputCoverage);
 
         // We may override color and coverage here if we have unform color or coverage.  This is
         // obviously not ideal.
         // TODO lets the GP itself do the override
         if (GrProgramDesc::kAttribute_ColorInput == header.fColorInput) {
             *inputColor = outputColor;
         }
-        if (GrProgramDesc::kUniform_ColorInput != header.fCoverageInput) {
-            *inputCoverage = outputCoverage;
+
+        // We may have uniform coverage, if so we need to multiply the GPs output by the uniform
+        // coverage
+        if (GrProgramDesc::kUniform_ColorInput == header.fCoverageInput) {
+            fFS.codeAppendf("%s *= %s;", outputCoverage.c_str(), inputCoverage->c_str());
         }
+        *inputCoverage = outputCoverage;
     }
 
     fFragmentProcessors.reset(SkNEW(GrGLInstalledFragProcs));
     int numProcs = fOptState.numFragmentStages();
     this->emitAndInstallFragProcs(0, fOptState.numColorStages(), inputColor);
     this->emitAndInstallFragProcs(fOptState.numColorStages(), numProcs,  inputCoverage);
 
     if (fOptState.hasGeometryProcessor()) {
         fVS.transformToNormalizedDeviceSpace();
     }
@@ skipping 331 matching lines @@
 }
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 
 GrGLInstalledFragProcs::~GrGLInstalledFragProcs() {
     int numProcs = fProcs.count();
     for (int e = 0; e < numProcs; ++e) {
         SkDELETE(fProcs[e]);
     }
 }