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

src/effects/gradients/SkLinearGradient.cpp

 
 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkLinearGradient.h"
 
@@ skipping 507 matching lines @@
 
 /////////////////////////////////////////////////////////////////////
 
 void GrGLLinearGradient::emitCode(GrGLShaderBuilder* builder,
                                   const GrDrawEffect&,
                                   EffectKey key,
                                   const char* outputColor,
                                   const char* inputColor,
                                   const TextureSamplerArray& samplers) {
     this->emitYCoordUniform(builder);
-    const char* coords;
+    SkString coords;
     this->setupMatrix(builder, key, &coords);
     SkString t;
     t.append(coords);
     t.append(".x");
     this->emitColorLookup(builder, t.c_str(), outputColor, inputColor, samplers[0]);
 }
 
 /////////////////////////////////////////////////////////////////////
 
 GrEffectRef* SkLinearGradient::asNewEffect(GrContext* context, const SkPaint&) const {
@@ skipping 20 matching lines @@
     str->append("SkLinearGradient (");
 
     str->appendf("start: (%f, %f)", fStart.fX, fStart.fY);
     str->appendf(" end: (%f, %f) ", fEnd.fX, fEnd.fY);
 
     this->INHERITED::toString(str);
 
     str->append(")");
 }
 #endif