Revert "Remove updatesCollectionView from grid view controller."

This reverts commit 28310fb5.

Reason for revert: [Sheriff] Failing deterministically on ios-simulator-noncq
Example: https://ci.chromium.org/p/chromium/builders/ci/ios-simulator-noncq/12130

Original change's description:
> Remove updatesCollectionView from grid view controller.
> 
> In order to allow the tab thumbnails to be up to date when the thumb
> strip is visible, the grid's collection view needs to be updated even
> when other view controllers are obscuring it. When selecting a new item
> from the collection view (blue highlight around the thumbnail), the item
> that is currently selected needs to be deselected to prevent multiple
> simultaneous selection.
> 
> Bug: 1127604
> Change-Id: Ic1e4a2dd4d0f2c269031b9d27b47b38c56b07a40
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2410494
> Reviewed-by: Gauthier Ambard <gambard@chromium.org>
> Commit-Queue: Roberto Moura <mouraroberto@google.com>
> Auto-Submit: Roberto Moura <mouraroberto@google.com>
> Cr-Commit-Position: refs/heads/master@{#809263}

TBR=gambard@chromium.org,mouraroberto@google.com

Change-Id: Ia7c8b2a2946424754838f5d2fdcd76d203745e59
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1127604
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2423170Reviewed-by: Leonard Grey <lgrey@chromium.org>
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809337}

ios/chrome/browser/ui/tab_grid/grid/grid_view_controller.mm

@@ -51,6 +51,11 @@ NSIndexPath* CreateIndexPath(NSInteger index) {
                                   UICollectionViewDelegate,
                                   UICollectionViewDragDelegate,
                                   UICollectionViewDropDelegate>
+// There is no need to update the collection view when other view controllers
+// are obscuring the collection view. Bookkeeping is based on |-viewWillAppear:|
+// and |-viewWillDisappear methods. Note that the |Did| methods are not reliably
+// called (e.g., edge case in multitasking).
+@property(nonatomic, assign) BOOL updatesCollectionView;
 // A collection view of items in a grid format.
 @property(nonatomic, weak) UICollectionView* collectionView;
 // The local model backing the collection view.
@@ -282,6 +287,7 @@ NSIndexPath* CreateIndexPath(NSInteger index) {
 }
 
 - (void)contentWillAppearAnimated:(BOOL)animated {
+  self.updatesCollectionView = YES;
   self.defaultLayout.animatesItemUpdates = YES;
   [self.collectionView reloadData];
   // Selection is invalid if there are no items.
@@ -299,6 +305,7 @@ NSIndexPath* CreateIndexPath(NSInteger index) {
 }
 
 - (void)contentWillDisappear {
+  self.updatesCollectionView = NO;
 }
 
 #pragma mark - UICollectionViewDataSource
@@ -522,14 +529,17 @@ NSIndexPath* CreateIndexPath(NSInteger index) {
 
   self.items = [items mutableCopy];
   self.selectedItemID = selectedItemID;
-  [self.collectionView reloadData];
-  [self.collectionView selectItemAtIndexPath:CreateIndexPath(self.selectedIndex)
-                                    animated:YES
-                              scrollPosition:UICollectionViewScrollPositionTop];
-  if (self.items.count > 0) {
-    [self removeEmptyStateAnimated:YES];
-  } else {
-    [self animateEmptyStateIn];
+  if ([self updatesCollectionView]) {
+    [self.collectionView reloadData];
+    [self.collectionView
+        selectItemAtIndexPath:CreateIndexPath(self.selectedIndex)
+                     animated:YES
+               scrollPosition:UICollectionViewScrollPositionTop];
+    if (self.items.count > 0) {
+      [self removeEmptyStateAnimated:YES];
+    } else {
+      [self animateEmptyStateIn];
+    }
   }
   // Whether the view is visible or not, the delegate must be updated.
   [self.delegate gridViewController:self didChangeItemCount:self.items.count];
@@ -608,13 +618,9 @@ NSIndexPath* CreateIndexPath(NSInteger index) {
 }
 
 - (void)selectItemWithID:(NSString*)selectedItemID {
-  if (self.selectedItemID == selectedItemID)
-    return;
-
-  [self.collectionView
-      deselectItemAtIndexPath:CreateIndexPath(self.selectedIndex)
-                     animated:YES];
   self.selectedItemID = selectedItemID;
+  if (!([self updatesCollectionView] && self.showsSelectionUpdates))
+    return;
   [self.collectionView
       selectItemAtIndexPath:CreateIndexPath(self.selectedIndex)
                    animated:YES
@@ -629,6 +635,8 @@ NSIndexPath* CreateIndexPath(NSInteger index) {
          [self indexOfItemWithID:item.identifier] == NSNotFound);
   NSUInteger index = [self indexOfItemWithID:itemID];
   self.items[index] = item;
+  if (![self updatesCollectionView])
+    return;
   GridCell* cell = base::mac::ObjCCastStrict<GridCell>(
       [self.collectionView cellForItemAtIndexPath:CreateIndexPath(index)]);
   // |cell| may be nil if it is scrolled offscreen.
@@ -705,13 +713,22 @@ NSIndexPath* CreateIndexPath(NSInteger index) {
 
 #pragma mark - Private
 
-// Performs model updates and view updates.
+// Performs model updates and view updates together if the view is appeared, or
+// only the model updates if the view is not appeared. |completion| is only run
+// if view is appeared.
 - (void)performModelUpdates:(ProceduralBlock)modelUpdates
               collectionViewUpdates:(ProceduralBlock)collectionViewUpdates
     collectionViewUpdatesCompletion:
         (ProceduralBlockWithBool)collectionViewUpdatesCompletion {
-  modelUpdates();
+  // If the view isn't visible, there's no need for the collection view to
+  // update.
+  if (![self updatesCollectionView]) {
+    modelUpdates();
+    return;
+  }
   [self.collectionView performBatchUpdates:^{
+    // Synchronize model and view updates.
+    modelUpdates();
     collectionViewUpdates();
   }
                                 completion:collectionViewUpdatesCompletion];

ios/chrome/browser/web/browsing_egtest.mm

@@ -77,13 +77,12 @@ class ReloadResponseProvider : public web::DataResponseProvider {
 
 @implementation BrowsingTestCase
 
-// Matcher for the title of the current tab (on tablet only), which is
-// sufficiently visible.
+// Matcher for the title of the current tab (on tablet only).
 id<GREYMatcher> TabWithTitle(const std::string& tab_title) {
   id<GREYMatcher> notPartOfOmnibox =
       grey_not(grey_ancestor(chrome_test_util::Omnibox()));
   return grey_allOf(grey_accessibilityLabel(base::SysUTF8ToNSString(tab_title)),
-                    notPartOfOmnibox, grey_sufficientlyVisible(), nil);
+                    notPartOfOmnibox, nil);
 }
 
 // Tests that page successfully reloads.
@@ -121,7 +120,7 @@ id<GREYMatcher> TabWithTitle(const std::string& tab_title) {
       destinationURL.spec().substr(destinationURL.scheme().length() + 3);
 
   [[EarlGrey selectElementWithMatcher:TabWithTitle(URLWithoutScheme)]
-      assertWithMatcher:grey_notNil()];
+      assertWithMatcher:grey_sufficientlyVisible()];
 }
 
 // Tests that after a PDF is loaded, the title appears in the tab bar on iPad.
@@ -139,7 +138,7 @@ id<GREYMatcher> TabWithTitle(const std::string& tab_title) {
       destinationURL.spec().substr(destinationURL.scheme().length() + 3);
 
   [[EarlGrey selectElementWithMatcher:TabWithTitle(URLWithoutScheme)]
-      assertWithMatcher:grey_notNil()];
+      assertWithMatcher:grey_sufficientlyVisible()];
 }
 
 // Tests that tab title is set to the specified title from a JavaScript.
@@ -156,7 +155,7 @@ id<GREYMatcher> TabWithTitle(const std::string& tab_title) {
   [ChromeEarlGrey loadURL:URL];
 
   [[EarlGrey selectElementWithMatcher:TabWithTitle(kPageTitle)]
-      assertWithMatcher:grey_notNil()];
+      assertWithMatcher:grey_sufficientlyVisible()];
 }
 
 // Tests clicking a link with target="_blank" and "event.stopPropagation()"