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

chrome/browser/safe_browsing/download_protection_service_unittest.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 "chrome/browser/safe_browsing/download_protection_service.h"
 
 #include <map>
 #include <string>
 
 #include "base/base_paths.h"
@@ skipping 372 matching lines @@
       base::Bind(&DownloadProtectionServiceTest::CheckDoneCallback,
                  base::Unretained(this)));
   msg_loop_.Run();
   EXPECT_TRUE(IsResult(DownloadProtectionService::SAFE));
 }
 
 TEST_F(DownloadProtectionServiceTest, CheckClientDownloadFetchFailed) {
   net::FakeURLFetcherFactory factory(NULL);
   // HTTP request will fail.
   factory.SetFakeResponse(
-      DownloadProtectionService::GetDownloadRequestUrl(), "", false);
+      DownloadProtectionService::GetDownloadRequestUrl(), std::string(), false);
 
   base::FilePath a_tmp(FILE_PATH_LITERAL("a.tmp"));
   base::FilePath a_exe(FILE_PATH_LITERAL("a.exe"));
   std::vector<GURL> url_chain;
   url_chain.push_back(GURL("http://www.evil.com/a.exe"));
   GURL referrer("http://www.google.com/");
   std::string hash = "hash";
 
   content::MockDownloadItem item;
   EXPECT_CALL(item, AddObserver(_));
@@ skipping 670 matching lines @@
   GetCertificateWhitelistStrings(*cert, *issuer_cert, &whitelist_strings);
   EXPECT_THAT(whitelist_strings, ElementsAre(cert_base + "/OU=unit"));
 
   cert = ReadTestCertificate("test_c.pem");
   ASSERT_TRUE(cert.get());
   whitelist_strings.clear();
   GetCertificateWhitelistStrings(*cert, *issuer_cert, &whitelist_strings);
   EXPECT_THAT(whitelist_strings, ElementsAre());
 }
 }  // namespace safe_browsing