Move FileEnumerator to its own file, do some refactoring.

remoting/host/policy_hack/policy_watcher_linux.cc

Index: remoting/host/policy_hack/policy_watcher_linux.cc
diff --git a/remoting/host/policy_hack/policy_watcher_linux.cc b/remoting/host/policy_hack/policy_watcher_linux.cc
index f3cffeafb0f0f7a050b8bb1f3085f7d6f4ff0434..f0bb9f5df4f8ab66da8f79d12522a4e37edf3317 100644
--- a/remoting/host/policy_hack/policy_watcher_linux.cc
+++ b/remoting/host/policy_hack/policy_watcher_linux.cc
@@ -17,6 +17,7 @@
 #include "base/bind.h"
 #include "base/compiler_specific.h"
 #include "base/file_util.h"
+#include "base/files/file_enumerator.h"
 #include "base/files/file_path.h"
 #include "base/files/file_path_watcher.h"
 #include "base/json/json_file_value_serializer.h"
@@ -108,9 +109,9 @@ class PolicyWatcherLinux : public PolicyWatcher {
     }
 
     // Enumerate the files and find the most recent modification timestamp.
-    file_util::FileEnumerator file_enumerator(config_dir_,
-                                              false,
-                                              file_util::FileEnumerator::FILES);
+    base::FileEnumerator file_enumerator(config_dir_,
+                                         false,
+                                         base::FileEnumerator::FILES);
     for (base::FilePath config_file = file_enumerator.Next();
          !config_file.empty();
          config_file = file_enumerator.Next()) {
@@ -129,8 +130,8 @@ class PolicyWatcherLinux : public PolicyWatcher {
     DCHECK(OnPolicyWatcherThread());
     // Enumerate the files and sort them lexicographically.
     std::set<base::FilePath> files;
-    file_util::FileEnumerator file_enumerator(config_dir_, false,
-                                              file_util::FileEnumerator::FILES);
+    base::FileEnumerator file_enumerator(config_dir_, false,
+                                         base::FileEnumerator::FILES);
     for (base::FilePath config_file_path = file_enumerator.Next();
          !config_file_path.empty(); config_file_path = file_enumerator.Next())
       files.insert(config_file_path);