Cleanup: Pass std::string as const reference if possible

gpu/tools/compositor_model_bench/shaders.cc

Index: gpu/tools/compositor_model_bench/shaders.cc
diff --git a/gpu/tools/compositor_model_bench/shaders.cc b/gpu/tools/compositor_model_bench/shaders.cc
index 5559e73a558d526707ef18b7298739b8fbdb43c3..66f5aac63e2b4cfbeeb4a4b84678edec22cc751e 100644
--- a/gpu/tools/compositor_model_bench/shaders.cc
+++ b/gpu/tools/compositor_model_bench/shaders.cc
@@ -81,7 +81,7 @@ static void TranslateInPlace(float* m, float tx, float ty, float tz) {
 
 ///////////////////////////////////////////////////////////////////////////////
 
-ShaderID ShaderIDFromString(std::string name) {
+ShaderID ShaderIDFromString(const std::string& name) {
   if (name == "VertexShaderPosTexYUVStretch")
     return VERTEX_SHADER_POS_TEX_YUV_STRETCH;
   if (name == "VertexShaderPosTex")