[124][iOS] Reset layout when activating voice over

VoiceOver scroll ability comes from a special handling of the layout
when VoiceOver is activated.
Invalidate the layout when voice over is turned on/off to make sure
the layout is correct.

(cherry picked from commit c16a454)

Fixed: 330856099
Change-Id: I1024de47dfa5030124eef29f335d3865946e8979
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5385657
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Auto-Submit: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Ewann Pellé <ewannpv@chromium.org>
Reviewed-by: Ewann Pellé <ewannpv@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1276830}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5385330
Cr-Commit-Position: refs/branch-heads/6367@{#203}
Cr-Branched-From: d158c6d-refs/heads/main@{#1274542}

Author: Gauthier Ambard

ios/chrome/browser/ui/tab_switcher/tab_strip/ui/tab_strip_layout.swift

@@ -47,6 +47,10 @@ class TabStripLayout: UICollectionViewFlowLayout {
       left: TabStripConstants.CollectionView.horizontalInset,
       bottom: 0,
       right: TabStripConstants.CollectionView.horizontalInset)
+
+    NotificationCenter.default.addObserver(
+      self, selector: #selector(voiceOverChanged),
+      name: UIAccessibility.voiceOverStatusDidChangeNotification, object: nil)
   }
 
   required init?(coder: NSCoder) {
@@ -565,6 +569,11 @@ class TabStripLayout: UICollectionViewFlowLayout {
     return alpha
   }
 
+  // Called when voice over is activated.
+  @objc func voiceOverChanged() {
+    self.invalidateLayout()
+  }
+
   // MARK: - Public
 
   // Calculates the dynamic size of a tab according to the number of tabs and