Force input coverage to be only a byte in gpu shaders.

src/gpu/gl/GrGLProgram.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef GrGLProgram_DEFINED
 #define GrGLProgram_DEFINED
@@ skipping 137 matching lines @@
     // Sets the texture units for samplers.
     void initSamplerUniforms();
     void initSamplers(GrGLInstalledProc*, int* texUnitIdx);
 
     // Helper for setData(). Makes GL calls to specify the initial color when there is not
     // per-vertex colors.
     void setColor(const GrOptDrawState&, GrColor color);
 
     // Helper for setData(). Makes GL calls to specify the initial coverage when there is not
     // per-vertex coverages.
-    void setCoverage(const GrOptDrawState&, GrColor coverage);
+    void setCoverage(const GrOptDrawState&, uint8_t coverage);
 
     // A templated helper to loop over effects, set the transforms(via subclass) and bind textures
     void setFragmentData(const GrOptDrawState&);
     virtual void setTransformData(const GrFragmentStage& effectStage, GrGLInstalledFragProc* pe);
     void bindTextures(const GrGLInstalledProc*, const GrProcessor&);
 
     /*
      * Legacy NVPR needs a hook here to flush path tex gen settings.
      * TODO when legacy nvpr is removed, remove this call.
      */
     virtual void didSetData(GrGpu::DrawType);
 
     // Helper for setData() that sets the view matrix and loads the render target height uniform
     void setMatrixAndRenderTargetHeight(GrGpu::DrawType, const GrOptDrawState&);
     virtual void onSetMatrixAndRenderTargetHeight(GrGpu::DrawType, const GrOptDrawState&);
 
     // these reflect the current values of uniforms (GL uniform values travel with program)
     MatrixState fMatrixState;
     GrColor fColor;
-    GrColor fCoverage;
+    uint8_t fCoverage;
     int fDstCopyTexUnit;
     BuiltinUniformHandles fBuiltinUniformHandles;
     GrGLuint fProgramID;
 
     // the installed effects
     SkAutoTDelete<GrGLInstalledGeoProc> fGeometryProcessor;
     SkAutoTUnref<GrGLInstalledFragProcs> fFragmentProcessors;
 
     GrProgramDesc fDesc;
     GrGpuGL* fGpu;
@@ skipping 70 matching lines @@
     virtual void setTransformData(const GrFragmentStage&, GrGLInstalledFragProc*) SK_OVERRIDE;
 
     int fTexCoordSetCnt;
 
     friend class GrGLLegacyNvprProgramBuilder;
 
     typedef GrGLNvprProgramBase INHERITED;
 };
 
 #endif