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

src/effects/SkMagnifierImageFilter.cpp

 /*
  * Copyright 2012 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 "SkBitmap.h"
 #include "SkMagnifierImageFilter.h"
 #include "SkColorPriv.h"
@@ skipping 109 matching lines @@
     : INHERITED(factory)
     , fEffectMatrix(drawEffect.castEffect<GrMagnifierEffect>().coordsType()) {
 }
 
 void GrGLMagnifierEffect::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);
     fOffsetVar = builder->addUniform(
         GrGLShaderBuilder::kFragment_ShaderType |
         GrGLShaderBuilder::kVertex_ShaderType,
         kVec2f_GrSLType, "uOffset");
     fZoomVar = builder->addUniform(
         GrGLShaderBuilder::kFragment_ShaderType |
         GrGLShaderBuilder::kVertex_ShaderType,
         kVec2f_GrSLType, "uZoom");
     fInsetVar = builder->addUniform(
         GrGLShaderBuilder::kFragment_ShaderType |
         GrGLShaderBuilder::kVertex_ShaderType,
         kVec2f_GrSLType, "uInset");
 
-    builder->fsCodeAppendf("\t\tvec2 coord = %s;\n", coords);
+    builder->fsCodeAppendf("\t\tvec2 coord = %s;\n", coords.c_str());
     builder->fsCodeAppendf("\t\tvec2 zoom_coord = %s + %s / %s;\n",
                            builder->getUniformCStr(fOffsetVar),
-                            coords,
+                           coords.c_str(),
                            builder->getUniformCStr(fZoomVar));
 
     builder->fsCodeAppend("\t\tvec2 delta = min(coord, vec2(1.0, 1.0) - coord);\n");
 
     builder->fsCodeAppendf("\t\tdelta = delta / %s;\n", builder->getUniformCStr(fInsetVar));
 
     builder->fsCodeAppend("\t\tfloat weight = 0.0;\n");
     builder->fsCodeAppend("\t\tif (delta.s < 2.0 && delta.t < 2.0) {\n");
     builder->fsCodeAppend("\t\t\tdelta = vec2(2.0, 2.0) - delta;\n");
     builder->fsCodeAppend("\t\t\tfloat dist = length(delta);\n");
@@ skipping 183 matching lines @@
 
             int x_val = SkMin32(SkScalarFloorToInt(x_interp), width - 1);
             int y_val = SkMin32(SkScalarFloorToInt(y_interp), height - 1);
 
             *dptr = sptr[y_val * width + x_val];
             dptr++;
         }
     }
     return true;
 }