Rewrite std::string("") to std::string(), Linux edition.

sandbox/linux/tests/unit_tests.cc

 // Copyright (c) 2012 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 <fcntl.h>
 #include <poll.h>
 #include <signal.h>
 #include <stdio.h>
 #include <sys/resource.h>
 #include <sys/time.h>
 #include <unistd.h>
 
 #include "base/file_util.h"
 #include "base/third_party/valgrind/valgrind.h"
 #include "sandbox/linux/tests/unit_tests.h"
 
 namespace {
 std::string TestFailedMessage(const std::string& msg) {
-  return msg.empty() ? "" : "Actual test failure: " + msg;
+  return msg.empty() ? std::string() : "Actual test failure: " + msg;
 }
 
 int GetSubProcessTimeoutTimeInSeconds() {
   // 10s ought to be enough for anybody.
   return 10;
 }
 
 // Returns the number of threads of the current process or -1.
 int CountThreads() {
   struct stat task_stat;
@@ skipping 189 matching lines @@
   fflush(stderr);
   _exit(kExitWithAssertionFailure);
 }
 
 void UnitTests::IgnoreThisTest() {
   fflush(stderr);
   _exit(kIgnoreThisTest);
 }
 
 }  // namespace