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

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 299 matching lines @@
     /**
      * Inserts code to implement the GrGradientEffect's matrix. This should be called before a
      * subclass emits its own code. The name of the 2D coords is output via fsCoordName and already
      * incorporates any perspective division. The caller can also optionally retrieve the name of
      * the varying inserted in the VS and its type, which may be either vec2f or vec3f depending
      * upon whether the matrix has perspective or not. It is not necessary to mask the key before
      * calling.
      */
     void setupMatrix(GrGLShaderBuilder* builder,
                      EffectKey key,
-                     const char** fsCoordName,
-                     const char** vsVaryingName = NULL,
+                     SkString* fsCoordName,
+                     SkString* vsVaryingName = NULL,
                      GrSLType* vsVaryingType = NULL);
 
     // Emits the uniform used as the y-coord to texture samples in derived classes. Subclasses
     // should call this method from their emitCode().
     void emitYCoordUniform(GrGLShaderBuilder* builder);
 
     // emit code that gets a fragment's color from an expression for t; for now this always uses the
     // texture, but for simpler cases we'll be able to lerp. Subclasses should call this method from
     // their emitCode().
     void emitColorLookup(GrGLShaderBuilder* builder,
                          const char* gradientTValue,
                          const char* outputColor,
                          const char* inputColor,
                          const GrGLShaderBuilder::TextureSampler&);
 
 private:
     static const GrEffect::CoordsType kCoordsType = GrEffect::kLocal_CoordsType;
 
     SkScalar fCachedYCoord;
     GrGLUniformManager::UniformHandle fFSYUni;
     GrGLEffectMatrix fEffectMatrix;
 
     typedef GrGLEffect INHERITED;
 };
 
 #endif
 
 #endif