create struct to hold all the params passed around for shader::context

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 235 matching lines @@
 
 void SkGradientShaderBase::flipGradientColors() {
     FlipGradientColors(fOrigColors, fRecs, fOrigColors, fRecs, fColorCount);
 }
 
 bool SkGradientShaderBase::isOpaque() const {
     return fColorsAreOpaque;
 }
 
 SkGradientShaderBase::GradientShaderBaseContext::GradientShaderBaseContext(
-        const SkGradientShaderBase& shader, const SkBitmap& device,
-        const SkPaint& paint, const SkMatrix& matrix)
-    : INHERITED(shader, device, paint, matrix)
+        const SkGradientShaderBase& shader, const ContextRec& rec)
+    : INHERITED(shader, rec)
     , fCache(shader.refCache(getPaintAlpha()))
 {
     const SkMatrix& inverse = this->getTotalInverse();
 
     fDstToIndex.setConcat(shader.fPtsToUnit, inverse);
 
     fDstToIndexProc = fDstToIndex.getMapXYProc();
     fDstToIndexClass = (uint8_t)SkShader::Context::ComputeMatrixClass(fDstToIndex);
 
     // now convert our colors in to PMColors
@@ skipping 942 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