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

src/gpu/gl/GrGLEffectMatrix.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 GrGLEffectMatrix_DEFINED
 #define GrGLEffectMatrix_DEFINED
 
@@ skipping 66 matching lines @@
                             CoordsType,
                             const GrTexture*);
 
     /**
      * Emits code to implement the matrix in the VS. A varying is added as an output of the VS and
      * input to the FS. The varying may be either a vec2f or vec3f depending upon whether
      * perspective interpolation is required or not. The names of the varying in the VS and FS are
      * are returned as output parameters and the type of the varying is the return value. The suffix
      * is an optional parameter that can be used to make all variables emitted by the object
      * unique within a stage. It is only necessary if multiple GrGLEffectMatrix objects are used by
-     * a GrGLEffect.
+     * a single GrGLEffect.
      */
     GrSLType emitCode(GrGLShaderBuilder*,
                       EffectKey,
-                      const char** fsCoordName, /* optional */
-                      const char** vsCoordName = NULL,
+                      SkString* fsCoordName, /* optional */
+                      SkString* vsCoordName = NULL,
                       const char* suffix = NULL);
 
     /**
      * This is similar to emitCode except that it performs perspective division in the FS if the
      * texture coordinates have a w coordinate. The fsCoordName always refers to a vec2f.
      */
     void emitCodeMakeFSCoords2D(GrGLShaderBuilder*,
                                 EffectKey,
-                                const char** fsCoordName, /* optional */
-                                const char** vsVaryingName = NULL,
+                                SkString* fsCoordName, /* optional */
+                                SkString* vsVaryingName = NULL,
                                 GrSLType* vsVaryingType = NULL,
                                 const char* suffix = NULL);
     /**
      * Call from a GrGLEffect's subclass to update the texture matrix. The effectMatrix and texture
      * params should match those used with GenKey.
      */
     void setData(const GrGLUniformManager& uniformManager,
                  const SkMatrix& effectMatrix,
                  const GrDrawEffect& drawEffect,
                  const GrTexture*);
 
     GrGLUniformManager::UniformHandle fUni;
     GrSLType                          fUniType;
     SkMatrix                          fPrevMatrix;
     CoordsType                        fCoordsType;
 };
 
 #endif