Shut up some Mac (xcode 3) warnings

Review URL: http://codereview.appspot.com/6503053/



git-svn-id: http://skia.googlecode.com/svn/trunk@5402 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/gl/GrGLProgram.cpp b/src/gpu/gl/GrGLProgram.cpp
index ff29bd4..664f1c0 100644
--- a/src/gpu/gl/GrGLProgram.cpp
+++ b/src/gpu/gl/GrGLProgram.cpp
@@ -947,7 +947,7 @@
     } else {
         uniforms.fTextureMatrixUni = builder->addUniform(GrGLShaderBuilder::kVertex_ShaderType,
                                                          kMat33f_GrSLType, "TexM", &matName);
-        const GrGLShaderVar& mat = builder->getUniformVariable(uniforms.fTextureMatrixUni);
+        builder->getUniformVariable(uniforms.fTextureMatrixUni);
 
         if (desc.fOptFlags & StageDesc::kNoPerspective_OptFlagBit) {
             texCoordVaryingType = kVec2f_GrSLType;