[iOS] Move banner a11y updates to util functions.

This will allow this functionality to be shared between overlay-based
and legacy infobar presentation.

Bug: 1030357
Change-Id: I3f3182cf41880ba03b5f4257936230238c72f8e9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1975016
Commit-Queue: Kurt Horimoto <kkhorimoto@chromium.org>
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#726440}

ios/chrome/browser/ui/infobars/banners/BUILD.gn

@@ -5,6 +5,8 @@
 source_set("banners") {
   configs += [ "//build/config/compiler:enable_arc" ]
   sources = [
+    "infobar_banner_accessibility_util.h",
+    "infobar_banner_accessibility_util.mm",
     "infobar_banner_consumer.h",
     "infobar_banner_delegate.h",
     "infobar_banner_view_controller.h",

ios/chrome/browser/ui/infobars/banners/infobar_banner_accessibility_util.h

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef IOS_CHROME_BROWSER_UI_INFOBARS_BANNERS_INFOBAR_BANNER_ACCESSIBILITY_UTIL_H_
+#define IOS_CHROME_BROWSER_UI_INFOBARS_BANNERS_INFOBAR_BANNER_ACCESSIBILITY_UTIL_H_
+
+#import <UIKit/UIKit.h>
+
+// Updates the accessibility of the presenting view controller so that VoiceOver
+// users have the ability to select other elements while the banner is
+// presented.  This should be called after the banner's presentation is
+// finished.  |presenting_view_controller| and |banner_view| must not be nil.
+void UpdateBannerAccessibilityForPresentation(
+    UIViewController* presenting_view_controller,
+    UIView* banner_view);
+
+// Removes the banner view from |presenting_view_controller|'s accessibility
+// elements.  This should be called after the banner's dismissal is finished.
+// |presenting_view_controller| must not be nil.
+void UpdateBannerAccessibilityForDismissal(
+    UIViewController* presenting_view_controller);
+
+#endif  // IOS_CHROME_BROWSER_UI_INFOBARS_BANNERS_INFOBAR_BANNER_ACCESSIBILITY_UTIL_H_

ios/chrome/browser/ui/infobars/banners/infobar_banner_accessibility_util.mm

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import "ios/chrome/browser/ui/infobars/banners/infobar_banner_accessibility_util.h"
+
+#include "base/logging.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+void UpdateBannerAccessibilityForPresentation(
+    UIViewController* presenting_view_controller,
+    UIView* banner_view) {
+  DCHECK(presenting_view_controller);
+  DCHECK(banner_view);
+  // Set the banner's superview accessibilityViewIsModal property to NO. This
+  // will allow the selection of the banner sibling views (e.g. the
+  // presentingViewController views).
+  banner_view.superview.accessibilityViewIsModal = NO;
+
+  // Make sure the banner is an accessibility element of
+  // |presenting_view_controller|.
+  presenting_view_controller.accessibilityElements =
+      @[ banner_view, presenting_view_controller.view ];
+
+  // Finally, focus the banner.
+  UIAccessibilityPostNotification(UIAccessibilityLayoutChangedNotification,
+                                  banner_view);
+}
+
+void UpdateBannerAccessibilityForDismissal(
+    UIViewController* presenting_view_controller) {
+  DCHECK(presenting_view_controller);
+  // Remove the Banner as an accessibility element.
+  presenting_view_controller.accessibilityElements =
+      @[ presenting_view_controller.view ];
+}

ios/chrome/browser/ui/infobars/coordinators/infobar_coordinator.mm

@@ -7,6 +7,7 @@
 #include "base/mac/foundation_util.h"
 #import "ios/chrome/browser/ui/fullscreen/animated_scoped_fullscreen_disabler.h"
 #import "ios/chrome/browser/ui/fullscreen/fullscreen_controller_factory.h"
+#import "ios/chrome/browser/ui/infobars/banners/infobar_banner_accessibility_util.h"
 #import "ios/chrome/browser/ui/infobars/banners/infobar_banner_presentation_state.h"
 #import "ios/chrome/browser/ui/infobars/coordinators/infobar_coordinator_implementation.h"
 #import "ios/chrome/browser/ui/infobars/infobar_badge_ui_delegate.h"
@@ -476,23 +477,10 @@ const CGFloat kiPadBannerOverlapWithOmnibox = 10.0;
             (UIViewController*)presentingViewController
                                              presenting:(BOOL)presenting {
   if (presenting) {
-    // Set the banner's superview accessibilityViewIsModal property to NO. This
-    // will allow the selection of the banner sibling views e.g. the
-    // presentingViewController views.
-    self.bannerViewController.view.superview.accessibilityViewIsModal = NO;
-
-    // Make sure the banner is an accessibility element of the
-    // PresentingViewController.
-    presentingViewController.accessibilityElements =
-        @[ self.bannerViewController.view, presentingViewController.view ];
-
-    // Finally, focus the banner.
-    UIAccessibilityPostNotification(UIAccessibilityLayoutChangedNotification,
-                                    self.bannerViewController.view);
+    UpdateBannerAccessibilityForPresentation(presentingViewController,
+                                             self.bannerViewController.view);
   } else {
-    // Remove the Banner as an A11y element.
-    presentingViewController.accessibilityElements =
-        @[ presentingViewController.view ];
+    UpdateBannerAccessibilityForDismissal(presentingViewController);
   }
 }