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

ui/compositor/layer.cc

Index: ui/compositor/layer.cc
diff --git a/ui/compositor/layer.cc b/ui/compositor/layer.cc
index 0c5543358f953af373914803cdbb84bcb7dd8305..352a9ce1e1e69e032cc691aa27e34589c2f07689 100644
--- a/ui/compositor/layer.cc
+++ b/ui/compositor/layer.cc
@@ -808,7 +808,7 @@ void Layer::SetForceRenderSurface(bool force) {
 
 class LayerDebugInfo : public base::trace_event::ConvertableToTraceFormat {
  public:
-  explicit LayerDebugInfo(std::string name) : name_(name) { }
+  explicit LayerDebugInfo(const std::string& name) : name_(name) {}
   void AppendAsTraceFormat(std::string* out) const override {
     base::DictionaryValue dictionary;
     dictionary.SetString("layer_name", name_);