[iOS] Makes bottom toolbar visible when modal view disappears

This Cl makes the bottom toolbar visible when initiating a drag down
to close a modal setting view.

Bug: 1106665
Change-Id: I2011d4e8f07c197c7c876bfc1dbbc40226d25f4d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2308713
Commit-Queue: Ewann Pellé <ewannpv@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Auto-Submit: Ewann Pellé <ewannpv@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791759}

ios/chrome/browser/ui/settings/settings_root_table_view_controller.mm

@@ -141,8 +141,8 @@ const CGFloat kActivityIndicatorDimensionIPhone = 56;
   }
 }
 
-- (void)viewWillDisappear:(BOOL)animated {
-  [super viewWillDisappear:animated];
+- (void)willMoveToParentViewController:(UIViewController*)parent {
+  [super willMoveToParentViewController:parent];
   [self.navigationController setToolbarHidden:YES animated:YES];
 }