Clarify GrGradientEffect key enum

src/effects/gradients/SkGradientShaderPriv.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkGradientShaderPriv_DEFINED
 #define SkGradientShaderPriv_DEFINED
 
@@ skipping 409 matching lines @@
                    GrGLSLUniformHandler* uniformHandler,
                    const GrGLSLCaps* caps,
                    const GrGradientEffect&,
                    const char* gradientTValue,
                    const char* outputColor,
                    const char* inputColor,
                    const SamplerHandle* texSamplers);
 
 private:
     enum {
-        kPremulTypeKeyBitCnt = 1,
-        kPremulTypeMask = 1,
-        kPremulBeforeInterpKey = kPremulTypeMask,
+        // First bit for premul before/after interp
+        kPremulBeforeInterpKey = 1,
 
-        kTwoColorKey = 2 << kPremulTypeKeyBitCnt,
-        kThreeColorKey = 3 << kPremulTypeKeyBitCnt,
-        kColorKeyMask = kTwoColorKey | kThreeColorKey,
-        kColorKeyBitCnt = 2,
-
-        // Subclasses must shift any key bits they produce up by this amount
-        // and combine with the result of GenBaseGradientKey.
-        kBaseKeyBitCnt = (kPremulTypeKeyBitCnt + kColorKeyBitCnt)
+        // Next two bits for 2/3 color type (neither means using texture atlas)
+        kTwoColorKey   = 4,
+        kThreeColorKey = 6,
     };
-    GR_STATIC_ASSERT(kBaseKeyBitCnt <= 32);
 
     SkScalar fCachedYCoord;
     GrGLSLProgramDataManager::UniformHandle fFSYUni;
     GrGLSLProgramDataManager::UniformHandle fColorStartUni;
     GrGLSLProgramDataManager::UniformHandle fColorMidUni;
     GrGLSLProgramDataManager::UniformHandle fColorEndUni;
 
     typedef GrGLSLFragmentProcessor INHERITED;
 };
 
 #endif
 
 #endif