Some GrGLShaderBuilder cleanup

Review URL: https://codereview.appspot.com/6500043/



git-svn-id: http://skia.googlecode.com/svn/trunk@5322 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/effects/GrConvolutionEffect.cpp b/src/gpu/effects/GrConvolutionEffect.cpp
index 2cefbc4..162a0cc 100644
--- a/src/gpu/effects/GrConvolutionEffect.cpp
+++ b/src/gpu/effects/GrConvolutionEffect.cpp
@@ -75,7 +75,7 @@
     const char* imgInc = builder->getUniformCStr(fImageIncrementUni);
 
     code->appendf("\t\tvec2 coord = %s - %d.0 * %s;\n",
-                  builder->fSampleCoords.c_str(), fRadius, imgInc);
+                  builder->defaultTexCoordsName(), fRadius, imgInc);
 
     // Manually unroll loop because some drivers don't; yields 20-30% speedup.
     for (int i = 0; i < width; i++) {