components: Move PrefRegistrySyncable into user_prefs namespace.

chrome/browser/download/download_prefs.h

Index: chrome/browser/download/download_prefs.h
diff --git a/chrome/browser/download/download_prefs.h b/chrome/browser/download/download_prefs.h
index e4f0fe03b2cebbb6e2fb2bb2959c4363884a5044..24b4446d3ae2d3528f4b8fdffd75ae235f3ff39d 100644
--- a/chrome/browser/download/download_prefs.h
+++ b/chrome/browser/download/download_prefs.h
@@ -10,7 +10,6 @@
 #include "base/files/file_path.h"
 #include "base/prefs/pref_member.h"
 
-class PrefRegistrySyncable;
 class PrefService;
 class Profile;
 
@@ -19,13 +18,17 @@ class BrowserContext;
 class DownloadManager;
 }
 
+namespace user_prefs {
+class PrefRegistrySyncable;
+}
+
 // Stores all download-related preferences.
 class DownloadPrefs {
  public:
   explicit DownloadPrefs(Profile* profile);
   ~DownloadPrefs();
 
-  static void RegisterUserPrefs(PrefRegistrySyncable* registry);
+  static void RegisterUserPrefs(user_prefs::PrefRegistrySyncable* registry);
 
   // Returns the DownloadPrefs corresponding to the given DownloadManager
   // or BrowserContext.