Fix case where GrGLEffectMatrix gives back a dangling ptr for the coords var name.

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 839 matching lines @@
 }
 
 GrGLEffect::EffectKey GrGLGradientEffect::GenMatrixKey(const GrDrawEffect& drawEffect) {
     const GrGradientEffect& e = drawEffect.castEffect<GrGradientEffect>();
     const GrTexture* texture = e.texture(0);
     return GrGLEffectMatrix::GenKey(e.getMatrix(), drawEffect, kCoordsType, texture);
 }
 
 void GrGLGradientEffect::setupMatrix(GrGLShaderBuilder* builder,
                                      EffectKey key,
-                                     const char** fsCoordName,
-                                     const char** vsVaryingName,
+                                     SkString* fsCoordName,
+                                     SkString* vsVaryingName,
                                      GrSLType* vsVaryingType) {
     fEffectMatrix.emitCodeMakeFSCoords2D(builder,
                                          key & kMatrixKeyMask,
                                          fsCoordName,
                                          vsVaryingName,
                                          vsVaryingType);
 }
 
 void GrGLGradientEffect::emitColorLookup(GrGLShaderBuilder* builder,
                                          const char* gradientTValue,
@@ skipping 104 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