[ios] Correct content suggestions safe area on rotation.

Various safe area tweaks to correct the layout of fakebox on rotation
when presented under another view controller.

Bug: 866864, 862208
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I7fda5c1ae564825c203566add4c7e738bcb38eb8
Reviewed-on: https://chromium-review.googlesource.com/1149100Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577826}

ios/chrome/browser/ui/content_suggestions/content_suggestions_header_synchronizer.mm

@@ -189,7 +189,14 @@ initWithCollectionController:
 - (void)updateFakeOmniboxOnNewWidth:(CGFloat)width {
   if (self.shouldAnimateHeader &&
       (IsUIRefreshPhase1Enabled() || !IsIPadIdiom())) {
-    UIEdgeInsets insets = SafeAreaInsetsForViewWithinNTP(self.collectionView);
+    // We check -superview here because in certain scenarios (such as when the
+    // VC is rotated underneath another presented VC), in a
+    // UICollectionViewController -viewSafeAreaInsetsDidChange the VC.view has
+    // updated safeAreaInsets, but VC.collectionView does not until a layer
+    // -viewDidLayoutSubviews.  Since self.collectionView and it's superview
+    // should always have the same safeArea, this should be safe.
+    UIEdgeInsets insets =
+        SafeAreaInsetsForViewWithinNTP(self.collectionView.superview);
     [self.headerController
         updateFakeOmniboxForOffset:self.collectionView.contentOffset.y
                        screenWidth:width

ios/chrome/browser/ui/content_suggestions/content_suggestions_view_controller.mm

@@ -310,6 +310,7 @@ BOOL ShouldCellsBeFullWidth(UITraitCollection* collection) {
   [super viewDidAppear:animated];
   // Resize the collection as it might have been rotated while not being
   // presented (e.g. rotation on stack view).
+  [self correctMissingSafeArea];
   [self updateConstraints];
   // Update the shadow bar.
   [self.audience contentOffsetDidChange];
@@ -354,6 +355,8 @@ BOOL ShouldCellsBeFullWidth(UITraitCollection* collection) {
 - (void)viewSafeAreaInsetsDidChange {
   [super viewSafeAreaInsetsDidChange];
   [self correctMissingSafeArea];
+  [self.headerSynchronizer
+      updateFakeOmniboxOnNewWidth:self.collectionView.bounds.size.width];
 }
 
 #pragma mark - UICollectionViewDelegate