[Hotword] Implement audio history pref accessing and setting.

chrome/browser/history/DEPS

 include_rules = [
   # History 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",
   "-components/search_engines",
   "+chrome/browser/chrome_notification_types.h",
   "+chrome/browser/common",
   "+chrome/browser/favicon",
   "+chrome/browser/history",
@@ skipping 23 matching lines @@
   "!chrome/browser/profiles/profile.h",
   "!chrome/browser/profiles/profile_manager.h",
   "!chrome/browser/signin/oauth2_token_service.h",
   "!chrome/browser/signin/profile_oauth2_token_service.h",
   "!chrome/browser/signin/profile_oauth2_token_service_factory.h",
   "!chrome/browser/signin/signin_manager.h",
   "!chrome/browser/signin/signin_manager_factory.h",
   "!chrome/browser/signin/token_service_factory.h",
   "!chrome/browser/sync/profile_sync_service.h",
   "!chrome/browser/sync/profile_sync_service_factory.h",
+  "!chrome/browser/sync/profile_sync_service_mock.h",
   "!chrome/browser/ui/browser.h",
   "!chrome/browser/ui/browser_finder.h",
   "!chrome/browser/ui/profile_error_dialog.h",
   "!chrome/browser/ui/webui/ntp/most_visited_handler.h",
   "!chrome/browser/ui/webui/ntp/new_tab_ui.h",
   "!components/bookmarks/browser/bookmark_model.h",
   "!components/bookmarks/browser/bookmark_utils.h",
   "!components/omnibox/autocomplete_match.h",
   "!components/omnibox/autocomplete_result.h",
   "!components/omnibox/url_prefix.h",
 ]
 
 specific_include_rules = {
   # Browser tests, by definition, need access to the browser objects.
   '.*_(api|browser|)test\.cc': [
     "+chrome/browser",
   ],
   # TODO(sdefresne): Bring this list to zero. http://crbug.com/370850
   #
   # Do not add to the list of temporarily-allowed dependencies below,
   # and please do not introduce more #includes of these files.
   '.*_[a-z]*test\.cc': [
     "!components/bookmarks/test/bookmark_test_helpers.h",
     "!components/bookmarks/test/test_bookmark_client.h",
   ]
 }