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

webkit/fileapi/local_file_system_cross_operation_unittest.cc

Index: webkit/fileapi/local_file_system_cross_operation_unittest.cc
diff --git a/webkit/fileapi/local_file_system_cross_operation_unittest.cc b/webkit/fileapi/local_file_system_cross_operation_unittest.cc
index 2929b9344a7b73164d6d12a95a2dda1ba77e909b..54660696ed0b8dc9a9f627887efbead716f90193 100644
--- a/webkit/fileapi/local_file_system_cross_operation_unittest.cc
+++ b/webkit/fileapi/local_file_system_cross_operation_unittest.cc
@@ -71,13 +71,11 @@ class CrossOperationTestHelper {
     FileSystemMountPointProvider* mount_point_provider =
         file_system_context_->GetMountPointProvider(src_type_);
     mount_point_provider->GetFileSystemRootPathOnFileThread(
-        SourceURL(""),
-        true /* create */);
+        SourceURL(std::string()), true /* create */);
     mount_point_provider =
         file_system_context_->GetMountPointProvider(dest_type_);
     mount_point_provider->GetFileSystemRootPathOnFileThread(
-        DestURL(""),
-        true /* create */);
+        DestURL(std::string()), true /* create */);
 
     // Grant relatively big quota initially.
     quota_manager_->SetQuota(origin_,