Extract most of the mutable state of SkShader into a separate Context object.

src/effects/gradients/SkGradientShader.cpp

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkGradientShaderPriv.h"
 #include "SkLinearGradient.h"
 #include "SkRadialGradient.h"
@@ skipping 206 matching lines @@
             buffer.writeUInt(recs[i].fScale);
         }
     }
     buffer.writeMatrix(fPtsToUnit);
 }
 
 bool SkGradientShaderBase::isOpaque() const {
     return fColorsAreOpaque;
 }
 
+#if 0
 bool SkGradientShaderBase::setContext(const SkBitmap& device,
                                  const SkPaint& paint,
                                  const SkMatrix& matrix) {
     if (!this->INHERITED::setContext(device, paint, matrix)) {
         return false;
     }
 
     const SkMatrix& inverse = this->getTotalInverse();
 
     if (!fDstToIndex.setConcat(fPtsToUnit, inverse)) {
@@ skipping 14 matching lines @@
     }
     // we can do span16 as long as our individual colors are opaque,
     // regardless of the paint's alpha
     if (fColorsAreOpaque) {
         fFlags |= kHasSpan16_Flag;
     }
 
     this->setCacheAlpha(paintAlpha);
     return true;
 }
+#endif
 
 void SkGradientShaderBase::setCacheAlpha(U8CPU alpha) const {
     // if the new alpha differs from the previous time we were called, inval our cache
     // this will trigger the cache to be rebuilt.
     // we don't care about the first time, since the cache ptrs will already be NULL
     if (fCacheAlpha != alpha) {
         fCache16 = NULL;            // inval the cache
         fCache32 = NULL;            // inval the cache
         fCacheAlpha = alpha;        // record the new alpha
         // inform our subclasses
@@ skipping 867 matching lines @@
             (*stops)[i] = stop;
             stop = i < outColors - 1 ? stop + random->nextUScalar1() * (1.f - stop) : 1.f;
         }
     }
     *tm = static_cast<SkShader::TileMode>(random->nextULessThan(SkShader::kTileModeCount));
 
     return outColors;
 }
 
 #endif