[iOS] Moving up the sign in buttons inside the safe area

Adding a fix that should have been committed with crrev.com/1286659

When the OK button layout is updated, the container layout should be
updated too.

Bug: 897105
Change-Id: I80a22e755d3255b4ce2c5f637280a3ac7576f1a5
Reviewed-on: https://chromium-review.googlesource.com/c/1290978Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Jérôme Lebel <jlebel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601137}

ios/chrome/browser/ui/first_run/welcome_to_chrome_view.mm

@@ -322,7 +322,7 @@ const char kPrivacyNoticeUrl[] = "internal://privacy-notice";
 
 - (void)safeAreaInsetsDidChange {
   [super safeAreaInsetsDidChange];
-  [self layoutOKButton];
+  [self layoutOKButtonAndContainerView];
 }
 
 - (void)layoutSubviews {
@@ -332,6 +332,10 @@ const char kPrivacyNoticeUrl[] = "internal://privacy-notice";
   [self layoutTOSLabel];
   [self layoutOptInLabel];
   [self layoutCheckBoxButton];
+  [self layoutOKButtonAndContainerView];
+}
+
+- (void)layoutOKButtonAndContainerView {
   // The OK Button must be laid out before the container view so that the
   // container view can take its position into account.
   [self layoutOKButton];