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

chrome/browser/autofill/DEPS

 include_rules = [
   # Autofill is being made into a Browser Component, so we have these basic
   # rules followed by temporary exceptions.  Please don't add to the list of
   # exceptions!
   "-chrome/browser",
   "+chrome/browser/api",
   "+chrome/browser/autofill",
   "+chrome/browser/common",
 
   # Permanently-allowed DEPS beyond the standard Browser
   # Components-like DEPS above go here.
   "+third_party/libphonenumber",  # For phone number i18n.
 
-  "+chrome/browser/prefs",
-
   # TODO(joi): May be able to remove this if PKS is moved to c/b/api.
   "!chrome/browser/profiles/profile_keyed_service.h",
 
   # TODO(akalin): Remove this dependency.
   "!sync/util/data_encryption_win.h",
 ]
 
 specific_include_rules = {
   # TODO(joi): Bring this list to zero.
   #
@@ skipping 25 matching lines @@
 
   # TODO(joi): May be able to get rid of the need for this by moving
   # PersonalDataManagerFactory to chrome/browser/profiles.
   'personal_data_manager_factory\.(h|cc)': [
     "!chrome/browser/profiles/profile_dependency_manager.h",
     "!chrome/browser/profiles/profile_keyed_service_factory.h",
     "!chrome/browser/profiles/profile.h",
     "!chrome/browser/webdata/web_data_service_factory.h",
   ],
 }