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

components/user_prefs/user_prefs_delegate.h

Index: components/user_prefs/user_prefs_delegate.h
diff --git a/components/user_prefs/user_prefs_delegate.h b/components/user_prefs/user_prefs_delegate.h
new file mode 100644
index 0000000000000000000000000000000000000000..54887933ed953b85eddb93ba19d424accc1d292e
--- /dev/null
+++ b/components/user_prefs/user_prefs_delegate.h
@@ -0,0 +1,27 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_USER_PREFS_USER_PREFS_DELEGATE_H_
+#define COMPONENTS_USER_PREFS_USER_PREFS_DELEGATE_H_
+
+class PrefService;
+
+namespace content {
+class BrowserContext;
+};
+
+namespace components {
+
+class UserPrefsDelegate {
+ public:
+  virtual ~UserPrefsDelegate() {}
+
+  // Return the PrefService associated with |context| or NULL if there is none.
+  virtual PrefService* PrefServiceFromBrowserContext(
+      content::BrowserContext* context) = 0;
+};
+
+}  // namespace components
+
+#endif  // COMPONENTS_USER_PREFS_USER_PREFS_DELEGATE_H_