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

src/gpu/effects/GrConvolutionEffect.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 "GrConvolutionEffect.h"
 #include "gl/GrGLEffect.h"
 #include "gl/GrGLEffectMatrix.h"
@@ skipping 44 matching lines @@
     fUseBounds = c.useBounds();
     fDirection = c.direction();
 }
 
 void GrGLConvolutionEffect::emitCode(GrGLShaderBuilder* builder,
                                      const GrDrawEffect&,
                                      EffectKey key,
                                      const char* outputColor,
                                      const char* inputColor,
                                      const TextureSamplerArray& samplers) {
-    const char* coords;
+    SkString coords;
     fEffectMatrix.emitCodeMakeFSCoords2D(builder, key, &coords);
     fImageIncrementUni = builder->addUniform(GrGLShaderBuilder::kFragment_ShaderType,
                                              kVec2f_GrSLType, "ImageIncrement");
     if (this->useBounds()) {
         fBoundsUni = builder->addUniform(GrGLShaderBuilder::kFragment_ShaderType,
                                          kVec2f_GrSLType, "Bounds");
     }
     fKernelUni = builder->addUniformArray(GrGLShaderBuilder::kFragment_ShaderType,
                                           kFloat_GrSLType, "Kernel", this->width());
 
     builder->fsCodeAppendf("\t\t%s = vec4(0, 0, 0, 0);\n", outputColor);
 
     int width = this->width();
     const GrGLShaderVar& kernel = builder->getUniformVariable(fKernelUni);
     const char* imgInc = builder->getUniformCStr(fImageIncrementUni);
 
-    builder->fsCodeAppendf("\t\tvec2 coord = %s - %d.0 * %s;\n", coords, fRadius, imgInc);
+    builder->fsCodeAppendf("\t\tvec2 coord = %s - %d.0 * %s;\n", coords.c_str(), fRadius, imgInc);
 
     // Manually unroll loop because some drivers don't; yields 20-30% speedup.
     for (int i = 0; i < width; i++) {
         SkString index;
         SkString kernelIndex;
         index.appendS32(i);
         kernel.appendArrayAccess(index.c_str(), &kernelIndex);
         builder->fsCodeAppendf("\t\t%s += ", outputColor);
         builder->appendTextureLookup(GrGLShaderBuilder::kFragment_ShaderType, samplers[0], "coord");
         if (this->useBounds()) {
@@ skipping 144 matching lines @@
     }
 
     bool useBounds = random->nextBool();
     return GrConvolutionEffect::Create(textures[texIdx],
                                        dir,
                                        radius,
                                        kernel,
                                        useBounds,
                                        bounds);
 }