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

remoting/host/native_messaging/native_messaging_reader_unittest.cc

 // Copyright 2013 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 "remoting/host/native_messaging/native_messaging_reader.h"
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 12 matching lines @@
   void SetUp() override;
 
   // Starts the reader and runs the MessageLoop to completion.
   void Run();
 
   // MessageCallback passed to the Reader. Stores |message| so it can be
   // verified by tests.
   void OnMessage(scoped_ptr<base::Value> message);
 
   // Writes a message (header+body) to the write-end of the pipe.
-  void WriteMessage(std::string message);
+  void WriteMessage(const std::string& message);
 
   // Writes some data to the write-end of the pipe.
   void WriteData(const char* data, int length);
 
  protected:
   scoped_ptr<NativeMessagingReader> reader_;
   base::File read_file_;
   base::File write_file_;
   scoped_ptr<base::Value> message_;
 
@@ skipping 23 matching lines @@
   reader_->Start(
       base::Bind(&NativeMessagingReaderTest::OnMessage, base::Unretained(this)),
       run_loop_.QuitClosure());
   run_loop_.Run();
 }
 
 void NativeMessagingReaderTest::OnMessage(scoped_ptr<base::Value> message) {
   message_ = message.Pass();
 }
 
-void NativeMessagingReaderTest::WriteMessage(std::string message) {
+void NativeMessagingReaderTest::WriteMessage(const std::string& message) {
   uint32 length = message.length();
   WriteData(reinterpret_cast<char*>(&length), 4);
   WriteData(message.data(), length);
 }
 
 void NativeMessagingReaderTest::WriteData(const char* data, int length) {
   int written = write_file_.WriteAtCurrentPos(data, length);
   ASSERT_EQ(length, written);
 }
 
@@ skipping 57 matching lines @@
   Run();
   EXPECT_TRUE(message_);
   base::DictionaryValue* message_dict;
   EXPECT_TRUE(message_->GetAsDictionary(&message_dict));
   int result;
   EXPECT_TRUE(message_dict->GetInteger("foo", &result));
   EXPECT_EQ(42, result);
 }
 
 }  // namespace remoting