Cleanup PreferenceMACs on browser_tests startup

base/files/scoped_temp_dir.cc

Index: base/files/scoped_temp_dir.cc
diff --git a/base/files/scoped_temp_dir.cc b/base/files/scoped_temp_dir.cc
index 26815217c6b46f07ab9540c349df33d2a726c898..a04e825156b6d1be7af531d38813f978a32be1d0 100644
--- a/base/files/scoped_temp_dir.cc
+++ b/base/files/scoped_temp_dir.cc
@@ -9,6 +9,13 @@
 
 namespace base {
 
+namespace {
+
+constexpr FilePath::CharType kScopedDirPrefix[] =
+    FILE_PATH_LITERAL("scoped_dir");
+
+}  // namespace
+
 ScopedTempDir::ScopedTempDir() {
 }
 
@@ -23,7 +30,7 @@ bool ScopedTempDir::CreateUniqueTempDir() {
 
   // This "scoped_dir" prefix is only used on Windows and serves as a template
   // for the unique name.
-  if (!base::CreateNewTempDirectory(FILE_PATH_LITERAL("scoped_dir"), &path_))
+  if (!base::CreateNewTempDirectory(kScopedDirPrefix, &path_))
     return false;
 
   return true;
@@ -38,9 +45,7 @@ bool ScopedTempDir::CreateUniqueTempDirUnderPath(const FilePath& base_path) {
     return false;
 
   // Create a new, uniquely named directory under |base_path|.
-  if (!base::CreateTemporaryDirInDir(base_path,
-                                     FILE_PATH_LITERAL("scoped_dir_"),
-                                     &path_))
+  if (!base::CreateTemporaryDirInDir(base_path, kScopedDirPrefix, &path_))
     return false;
 
   return true;
@@ -85,4 +90,9 @@ bool ScopedTempDir::IsValid() const {
   return !path_.empty() && DirectoryExists(path_);
 }
 
+// static
+const FilePath::CharType* ScopedTempDir::GetTempDirPrefix() {
+  return kScopedDirPrefix;
+}
+
 }  // namespace base