[iOS] Adding user action metrics when signing in

For some reasons, those metrics were not implemented for
sign-in before unity.
  + Signin_Signin_WithDefaultSyncSettings
  + Signin_Signin_WithAdvancedSyncSettings

This patch adds implementations for those 2 metrics for pre-unity
and unity code.

Also "Signin_Undo_Signin" is added for unity code (already implemented)
with pre-unity.

Bug: 937820
Change-Id: I27ec9769e9954b1daeccd273f4d663c35f9fa605
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1496981Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Jérôme Lebel <jlebel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#637585}

ios/chrome/browser/ui/authentication/chrome_signin_view_controller.mm

@@ -252,6 +252,13 @@ enum AuthenticationState {
 
 - (void)acceptSignInAndShowAccountsSettings:(BOOL)showAccountsSettings {
   signin_metrics::LogSigninAccessPointCompleted(_accessPoint, _promoAction);
+  if (showAccountsSettings) {
+    base::RecordAction(
+        base::UserMetricsAction("Signin_Signin_WithAdvancedSyncSettings"));
+  } else {
+    base::RecordAction(
+        base::UserMetricsAction("Signin_Signin_WithDefaultSyncSettings"));
+  }
   std::vector<int> consent_text_ids;
   int openSettingsStringId = -1;
   if (_unifiedConsentEnabled) {
@@ -991,6 +998,9 @@ enum AuthenticationState {
       return;
     case IDENTITY_PICKER_STATE:
       if (!_didFinishSignIn) {
+        if (_unifiedConsentEnabled) {
+          base::RecordAction(base::UserMetricsAction("Signin_Undo_Signin"));
+        }
         _didFinishSignIn = YES;
         [_delegate didSkipSignIn:self];
       }