Introduce //components/user_prefs, use to eliminate c/b/prefs dependency in Autofill.

base/prefs/pref_service.h

Index: base/prefs/pref_service.h
diff --git a/base/prefs/pref_service.h b/base/prefs/pref_service.h
index d9cc8f5f1ce3fe65b792c4d0921476da3f083f48..fb3b5844d51607c0e4e01849b80a7f6533248ac7 100644
--- a/base/prefs/pref_service.h
+++ b/base/prefs/pref_service.h
@@ -36,10 +36,6 @@ namespace base {
 class FilePath;
 }
 
-namespace content {
-class BrowserContext;
-}
-
 namespace subtle {
 class PrefMemberBase;
 class ScopedUserPrefUpdateBase;
@@ -349,10 +345,4 @@ class BASE_PREFS_EXPORT PrefService : public base::NonThreadSafe {
   DISALLOW_COPY_AND_ASSIGN(PrefService);
 };
 
-// Retrieves a PrefService for the given context.
-//
-// TODO(joi): This doesn't really belong here, since it references a
-// content type; probably best to get rid of it completely.
-PrefService* PrefServiceFromBrowserContext(content::BrowserContext* context);
-
 #endif  // BASE_PREFS_PREF_SERVICE_H_