Create swizzle table inside of glsl caps

include/gpu/GrContextOptions.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrContextOptions_DEFINED
 #define GrContextOptions_DEFINED
 
 #include "SkTypes.h"
 
 struct GrContextOptions {
     GrContextOptions()
         : fDrawPathToCompressedTexture(false)
         , fSuppressPrints(false)
         , fMaxTextureSizeOverride(SK_MaxS32)
         , fSuppressDualSourceBlending(false)
         , fGeometryBufferMapThreshold(-1)
         , fUseDrawInsteadOfPartialRenderTargetWrite(false)
-        , fImmediateMode(false) {}
+        , fImmediateMode(false)
+        , fUseShaderSwizzling(false) {}
 
     // EXPERIMENTAL
     // May be removed in the future, or may become standard depending
     // on the outcomes of a variety of internal tests.
     bool fDrawPathToCompressedTexture;
 
     // Suppress prints for the GrContext.
     bool fSuppressPrints;
 
     /** Overrides: These options override feature detection using backend API queries. These
         overrides can only reduce the feature set or limits, never increase them beyond the
         detected values. */
 
     int  fMaxTextureSizeOverride;
     bool fSuppressDualSourceBlending;
 
     /** the threshold in bytes above which we will use a buffer mapping API to map vertex and index
         buffers to CPU memory in order to update them.  A value of -1 means the GrContext should
         deduce the optimal value for this platform. */
     int  fGeometryBufferMapThreshold;
 
     /** some gpus have problems with partial writes of the rendertarget */
     bool fUseDrawInsteadOfPartialRenderTargetWrite;
 
     /** The GrContext operates in immedidate mode. It will issue all draws to the backend API
         immediately. Intended to ease debugging. */
     bool fImmediateMode;
+
+    /** Force us to do all swizzling manually in the shader and don't rely on extensions to do
+        swizzling. */
+    bool fUseShaderSwizzling;
 };
 
 #endif