Remove unused fields of ChromeBrowserStateIOData

Those fields are never accessed after initialization (except for
destruction). Remove the fields also track preferences that are
unused on iOS (they are related to managed accounts which is not
supported on iOS).

Bug: none
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I13f86b143d34fd0ba07d4372ff0e37133e0e2213
Reviewed-on: https://chromium-review.googlesource.com/1097334
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567211}

ios/chrome/browser/browser_state/BUILD.gn

@@ -75,7 +75,6 @@ source_set("browser_state_impl") {
     "//components/proxy_config/ios",
     "//components/signin/core/browser",
     "//components/signin/ios/browser:active_state_manager",
-    "//components/sync",
     "//components/sync_preferences",
     "//components/user_prefs",
     "//google_apis",

ios/chrome/browser/browser_state/chrome_browser_state_io_data.h

@@ -279,8 +279,6 @@ class ChromeBrowserStateIOData {
   // Member variables which are pointed to by the various context objects.
   mutable BooleanPrefMember enable_referrers_;
   mutable BooleanPrefMember enable_do_not_track_;
-  mutable BooleanPrefMember sync_disabled_;
-  mutable BooleanPrefMember signin_allowed_;
 
   BooleanPrefMember enable_metrics_;
 

ios/chrome/browser/browser_state/chrome_browser_state_io_data.mm

@@ -34,7 +34,6 @@
 #include "components/prefs/pref_service.h"
 #include "components/proxy_config/ios/proxy_service_factory.h"
 #include "components/signin/core/browser/signin_pref_names.h"
-#include "components/sync/base/pref_names.h"
 #include "ios/chrome/browser/application_context.h"
 #include "ios/chrome/browser/browser_state/chrome_browser_state.h"
 #include "ios/chrome/browser/chrome_url_constants.h"
@@ -126,12 +125,6 @@ void ChromeBrowserStateIOData::InitializeOnUIThread(
     google_services_user_account_id_.Init(prefs::kGoogleServicesUserAccountId,
                                           pref_service);
     google_services_user_account_id_.MoveToThread(io_task_runner);
-
-    sync_disabled_.Init(syncer::prefs::kSyncManaged, pref_service);
-    sync_disabled_.MoveToThread(io_task_runner);
-
-    signin_allowed_.Init(prefs::kSigninAllowed, pref_service);
-    signin_allowed_.MoveToThread(io_task_runner);
   }
 }
 
@@ -460,8 +453,6 @@ void ChromeBrowserStateIOData::ShutdownOnUIThread(
   enable_referrers_.Destroy();
   enable_do_not_track_.Destroy();
   enable_metrics_.Destroy();
-  sync_disabled_.Destroy();
-  signin_allowed_.Destroy();
   if (chrome_http_user_agent_settings_)
     chrome_http_user_agent_settings_->CleanupOnUIThread();