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

base/file_util_unittest.cc

Index: base/file_util_unittest.cc
diff --git a/base/file_util_unittest.cc b/base/file_util_unittest.cc
index 1f10a3353bd8dae5fdec0372a9972172e563437b..77dd7ac4f285c3107e9ec2777ff78cfc700886a7 100644
--- a/base/file_util_unittest.cc
+++ b/base/file_util_unittest.cc
@@ -1846,15 +1846,14 @@ TEST_F(FileUtilTest, FileEnumeratorTest) {
 
   // create the files
   FilePath dir2file = dir2.Append(FILE_PATH_LITERAL("dir2file.txt"));
-  CreateTextFile(dir2file, L"");
+  CreateTextFile(dir2file, std::wstring());
   FilePath dir2innerfile = dir2inner.Append(FILE_PATH_LITERAL("innerfile.txt"));
-  CreateTextFile(dir2innerfile, L"");
+  CreateTextFile(dir2innerfile, std::wstring());
   FilePath file1 = temp_dir_.path().Append(FILE_PATH_LITERAL("file1.txt"));
-  CreateTextFile(file1, L"");
-  FilePath file2_rel =
-      dir2.Append(FilePath::kParentDirectory)
-          .Append(FILE_PATH_LITERAL("file2.txt"));
-  CreateTextFile(file2_rel, L"");
+  CreateTextFile(file1, std::wstring());
+  FilePath file2_rel = dir2.Append(FilePath::kParentDirectory)
+      .Append(FILE_PATH_LITERAL("file2.txt"));
+  CreateTextFile(file2_rel, std::wstring());
   FilePath file2_abs = temp_dir_.path().Append(FILE_PATH_LITERAL("file2.txt"));
 
   // Only enumerate files.