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

chrome/common/extensions/extension_unittest.cc

 // Copyright (c) 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 "chrome/common/extensions/extension_unittest.h"
 
 #include "base/command_line.h"
 #include "base/file_util.h"
 #include "base/files/file_path.h"
 #include "base/format_macros.h"
@@ skipping 215 matching lines @@
 // actual crx files that we test other parts of the system with.
 TEST_F(ExtensionTest, MimeTypeSniffing) {
   base::FilePath path;
   ASSERT_TRUE(PathService::Get(chrome::DIR_TEST_DATA, &path));
   path = path.AppendASCII("extensions").AppendASCII("good.crx");
 
   std::string data;
   ASSERT_TRUE(file_util::ReadFileToString(path, &data));
 
   std::string result;
-  EXPECT_TRUE(net::SniffMimeType(data.c_str(), data.size(),
-              GURL("http://www.example.com/foo.crx"), "", &result));
+  EXPECT_TRUE(net::SniffMimeType(data.c_str(),
+                                 data.size(),
+                                 GURL("http://www.example.com/foo.crx"),
+                                 std::string(),
+                                 &result));
   EXPECT_EQ(std::string(Extension::kMimeType), result);
 
   data.clear();
   result.clear();
   path = path.DirName().AppendASCII("bad_magic.crx");
   ASSERT_TRUE(file_util::ReadFileToString(path, &data));
-  EXPECT_TRUE(net::SniffMimeType(data.c_str(), data.size(),
-              GURL("http://www.example.com/foo.crx"), "", &result));
+  EXPECT_TRUE(net::SniffMimeType(data.c_str(),
+                                 data.size(),
+                                 GURL("http://www.example.com/foo.crx"),
+                                 std::string(),
+                                 &result));
   EXPECT_EQ("application/octet-stream", result);
 }
 
 TEST_F(ExtensionTest, EffectiveHostPermissions) {
   (new ContentScriptsHandler)->Register();
   scoped_refptr<Extension> extension;
   URLPatternSet hosts;
 
   extension = LoadManifest("effective_host_permissions", "empty.json");
   EXPECT_EQ(0u, extension->GetEffectiveHostPermissions().patterns().size());
@@ skipping 685 matching lines @@
   error.clear();
   extension = LoadManifestUnchecked("optional_only_permission",
                                     "manifest2.json",
                                     Manifest::INTERNAL, Extension::NO_FLAGS,
                                     &error);
   EXPECT_TRUE(extension != NULL);
   EXPECT_TRUE(error.empty());
 }
 
 }  // namespace extensions