Use explicitly-sized enums in GrGLProgramDesc::KeyHeader

src/gpu/gl/GrGLProgramDesc.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGLProgramDesc_DEFINED
 #define GrGLProgramDesc_DEFINED
 
@@ skipping 136 matching lines @@
         GrGLShaderBuilder::DstReadKey fDstReadKey;      // set by GrGLShaderBuilder if there
                                                         // are effects that must read the dst.
                                                         // Otherwise, 0.
         GrGLShaderBuilder::FragPosKey fFragPosKey;      // set by GrGLShaderBuilder if there are
                                                         // effects that read the fragment position.
                                                         // Otherwise, 0.
 
         // should the FS discard if the coverage is zero (to avoid stencil manipulation)
         SkBool8                     fDiscardIfZeroCoverage;
 
-        uint8_t                     fColorInput;            // casts to enum ColorInput
-        uint8_t                     fCoverageInput;         // casts to enum ColorInput
-        uint8_t                     fCoverageOutput;        // casts to enum CoverageOutput
+        ColorInput                  fColorInput : 8;
+        ColorInput                  fCoverageInput : 8;
+        CoverageOutput              fCoverageOutput : 8;
 
         SkBool8                     fHasVertexCode;
         SkBool8                     fEmitsPointSize;
-        uint8_t                     fColorFilterXfermode;   // casts to enum SkXfermode::Mode
+        SkXfermode::Mode            fColorFilterXfermode : 8;
 
         // To enable experimental geometry shader code (not for use in
         // production)
 #if GR_GL_EXPERIMENTAL_GS
         SkBool8                     fExperimentalGS;
 #endif
 
         int8_t                      fPositionAttributeIndex;
         int8_t                      fLocalCoordAttributeIndex;
         int8_t                      fColorAttributeIndex;
@@ skipping 43 matching lines @@
     SkAutoSMalloc<kPreAllocSize> fKey;
     bool fInitialized;
 
     // GrGLProgram and GrGLShaderBuilder read the private fields to generate code. TODO: Move all
     // code generation to GrGLShaderBuilder (and maybe add getters rather than friending).
     friend class GrGLProgram;
     friend class GrGLShaderBuilder;
 };
 
 #endif