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

chrome/browser/themes/theme_syncable_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/themes/theme_syncable_service.h"
 
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
 #include "base/files/file_path.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 86 matching lines @@
   }
 
   virtual bool UsingNativeTheme() const OVERRIDE {
     return using_native_theme_;
   }
 
   virtual string GetThemeID() const OVERRIDE {
     if (theme_extension_)
       return theme_extension_->id();
     else
-      return "";
+      return std::string();
   }
 
   const extensions::Extension* theme_extension() const {
     return theme_extension_.get();
   }
 
   bool is_dirty() const {
     return is_dirty_;
   }
 
@@ skipping 477 matching lines @@
 
 TEST_F(PolicyInstalledThemeTest, InstallThemeByPolicy) {
   // Set up theme service to use custom theme that was installed by policy.
   fake_theme_service_->SetTheme(theme_extension_.get());
 
   syncer::SyncDataList data_list =
       theme_sync_service_->GetAllSyncData(syncer::THEMES);
 
   ASSERT_EQ(0u, data_list.size());
 }