[sync] Eliminate reload loop in sync settings page

During initial sync setup, if the user refreshes the settings page when
the advanced settings page is visible, and then hits the back button, we
enter a page reload loop.

A couple of salient features of the loop are:

1) When the back button is pressed, SyncSetupHandler::CloseSyncSetup()
   is called, which causes ProfileSyncService::NotifyObservers() to
   again indirectly call SyncSetupHandler::CloseSyncSetup(), due to
   SigninTracker::OnStateChanged() incorrectly detecting a signin
   failure.
2) When the sync setup page is loaded, SyncSetupHandler::OpenSyncSetup()
   calls OptionsSyncSetupHandler::ShowSetupUI(), resulting in an
   unnecessary navigation to chrome://settings/syncSetup, given that we
   are already at the sync setup page.

This patch does a few things to eliminate reload loops:

1) Removes SyncSetupHandler::ShowSetupUI(), and eliminates the derived
   class OptionsSyncSetupHandler. With web based sign in, there is no
   longer the need for SyncSetupHandler to re-navigate to
   chrome://settings/syncSetup.
2) In SyncSetupHandler::CloseSyncSetup(), we clear SigninTracker
   before potentially aborting sync setup. This eliminates the case
   where SigninTracker detects an abandoned sync setup as a signin
   failure.
3) In ProfileSyncService::SetSetupInProgress(), we only call
   NotifyObservers() if the value of |setup_in_progress_| changes.
   This eliminates additional recursive calls to
   SyncSetupHandler::CloseSyncSetup() in cases where it is called in
   response to ProfileSyncService::NotifyObservers() originating from
   ProfileSyncService::SetSetupInProgress().

BUG=245219
TEST=Repro steps in the above bug shouldn't result in a reload loop

Review URL: https://chromiumcodereview.appspot.com/16085012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@204217 0039d316-1c4b-4281-b951-d872f2087c98

0 files changed, 0 insertions, 0 deletions