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

components/test_runner/test_runner.h

 // 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.
 
 #ifndef COMPONENTS_TEST_RUNNER_TEST_RUNNER_H_
 #define COMPONENTS_TEST_RUNNER_TEST_RUNNER_H_
 
 #include <deque>
 #include <set>
 #include <string>
@@ skipping 69 matching lines @@
   std:: string customDumpText() const;
   bool shouldDumpAsMarkup();
   bool shouldDumpChildFrameScrollPositions() const;
   bool shouldDumpChildFramesAsMarkup() const;
   bool shouldDumpChildFramesAsText() const;
   void ShowDevTools(const std::string& settings,
                     const std::string& frontend_url);
   void ClearDevToolsLocalStorage();
   void setShouldDumpAsText(bool);
   void setShouldDumpAsMarkup(bool);
-  void setCustomTextOutput(std::string text);
+  void setCustomTextOutput(const std::string& text);
   void setShouldGeneratePixelResults(bool);
   void setShouldDumpFrameLoadCallbacks(bool);
   void setShouldDumpPingLoaderCallbacks(bool);
   void setShouldEnableViewSource(bool);
   bool shouldDumpEditingCallbacks() const;
   bool shouldDumpFrameLoadCallbacks() const;
   bool shouldDumpPingLoaderCallbacks() const;
   bool shouldDumpUserGestureInFrameLoadCallbacks() const;
   bool shouldDumpTitleChanges() const;
   bool shouldDumpIconChanges() const;
@@ skipping 221 matching lines @@
   ///////////////////////////////////////////////////////////////////////////
   // Methods modifying WebPreferences.
 
   // Set the WebPreference that controls webkit's popup blocking.
   void SetPopupBlockingEnabled(bool block_popups);
 
   void SetJavaScriptCanAccessClipboard(bool can_access);
   void SetXSSAuditorEnabled(bool enabled);
   void SetAllowUniversalAccessFromFileURLs(bool allow);
   void SetAllowFileAccessFromFileURLs(bool allow);
-  void OverridePreference(const std::string key, v8::Local<v8::Value> value);
+  void OverridePreference(const std::string& key, v8::Local<v8::Value> value);
 
   // Modify accept_languages in RendererPreferences.
   void SetAcceptLanguages(const std::string& accept_languages);
 
   // Enable or disable plugins.
   void SetPluginsEnabled(bool enabled);
 
   ///////////////////////////////////////////////////////////////////////////
   // Methods that modify the state of TestRunner
 
@@ skipping 490 matching lines @@
   bool use_mock_theme_;
 
   base::WeakPtrFactory<TestRunner> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TestRunner);
 };
 
 }  // namespace test_runner
 
 #endif  // COMPONENTS_TEST_RUNNER_TEST_RUNNER_H_