[DevTools] DevToolsUIBindings::CallClientFunction - reduce number of string copyings

chrome/browser/devtools/devtools_ui_bindings.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/devtools/devtools_ui_bindings.h"
 
 #include "base/command_line.h"
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
 #include "base/metrics/histogram.h"
@@ skipping 850 matching lines @@
 }
 
 bool DevToolsUIBindings::IsAttachedTo(content::DevToolsAgentHost* agent_host) {
   return agent_host_.get() == agent_host;
 }
 
 void DevToolsUIBindings::CallClientFunction(const std::string& function_name,
                                             const base::Value* arg1,
                                             const base::Value* arg2,
                                             const base::Value* arg3) {
-  std::string params;
+  std::string javascript = function_name + "(";
   if (arg1) {
     std::string json;
     base::JSONWriter::Write(arg1, &json);
-    params.append(json);
+    javascript.append(json);
     if (arg2) {
       base::JSONWriter::Write(arg2, &json);
-      params.append(", " + json);
+      javascript.append(", ").append(json);
       if (arg3) {
         base::JSONWriter::Write(arg3, &json);
-        params.append(", " + json);
+        javascript.append(", ").append(json);
       }
     }
   }
-
-  base::string16 javascript = base::UTF8ToUTF16(
-      function_name + "(" + params + ");");
-  web_contents_->GetMainFrame()->ExecuteJavaScript(javascript);
+  javascript.append(");");
+  web_contents_->GetMainFrame()->ExecuteJavaScript(
+      base::UTF8ToUTF16(javascript));
 }
 
 void DevToolsUIBindings::DocumentOnLoadCompletedInMainFrame() {
   // In the DEBUG_DEVTOOLS mode, the DocumentOnLoadCompletedInMainFrame event
   // arrives before the LoadCompleted event, thus it should not trigger the
   // frontend load handling.
 #if !defined(DEBUG_DEVTOOLS)
   FrontendLoaded();
 #endif
 }
 
 void DevToolsUIBindings::DidNavigateMainFrame() {
   frontend_loaded_ = false;
 }
 
 void DevToolsUIBindings::FrontendLoaded() {
   if (frontend_loaded_)
     return;
   frontend_loaded_ = true;
 
   // Call delegate first - it seeds importants bit of information.
   delegate_->OnLoadCompleted();
 
   UpdateTheme();
   AddDevToolsExtensionsToClient();
 }