Fixes content position so that its more accurate when restoring from

cache.

TBR=martiw

Bug: 695749
Change-Id: I9f7eb9b56cd608174c658ceffd1079eca7c10c04
Reviewed-on: https://chromium-review.googlesource.com/670963Reviewed-by: Ramya Sharma <ramyasharma@chromium.org>
Reviewed-by: Marti Wong <martiw@chromium.org>
Commit-Queue: Ramya Sharma <ramyasharma@chromium.org>
Cr-Commit-Position: refs/heads/master@{#502569}

ios/chrome/browser/ui/bookmarks/bookmark_home_handset_view_controller.mm

@@ -129,8 +129,6 @@ using bookmarks::BookmarkNode;
 - (void)viewWillLayoutSubviews {
   [super viewWillLayoutSubviews];
   if (base::FeatureList::IsEnabled(kBookmarkNewGeneration)) {
-    // TODO(crbug.com/695749): See if we need to store/restore the content
-    // scroll position for BookmarkTableView here.
     return;
   }
 

ios/chrome/browser/ui/bookmarks/bookmark_home_view_controller.mm

@@ -182,11 +182,23 @@ std::vector<GURL> GetUrlsToOpen(const std::vector<const BookmarkNode*>& nodes) {
 }
 
 - (void)viewWillAppear:(BOOL)animated {
+  [super viewWillAppear:animated];
   if (self.isReconstructingFromCache) {
     [self setupUIStackCacheIfApplicable];
   }
 }
 
+- (void)viewDidLayoutSubviews {
+  // Set the content position after views are laid out,
+  // to ensure the right window of rows is shown. Once
+  // used, reset self.cachedContentPosition.
+  if (self.cachedContentPosition) {
+    [self.bookmarksTableView
+        setContentPosition:self.cachedContentPosition.floatValue];
+    self.cachedContentPosition = nil;
+  }
+}
+
 #pragma mark - Public
 
 - (void)dismissModals {
@@ -975,10 +987,6 @@ std::vector<GURL> GetUrlsToOpen(const std::vector<const BookmarkNode*>& nodes) {
       setAutoresizingMask:UIViewAutoresizingFlexibleWidth |
                           UIViewAutoresizingFlexibleHeight];
   [self.bookmarksTableView setTranslatesAutoresizingMaskIntoConstraints:NO];
-  if (self.cachedContentPosition) {
-    [self.bookmarksTableView
-        setContentPosition:self.cachedContentPosition.floatValue];
-  }
   [self.view addSubview:self.bookmarksTableView];
 
   if (_rootNode != self.bookmarks->root_node()) {

ios/chrome/browser/ui/bookmarks/bookmark_table_view.mm

@@ -292,9 +292,13 @@ using IntegerPair = std::pair<NSInteger, NSInteger>;
 - (void)setContentPosition:(CGFloat)position {
   NSIndexPath* path =
       [NSIndexPath indexPathForRow:position inSection:self.bookmarksSection];
-  [self.tableView scrollToRowAtIndexPath:path
-                        atScrollPosition:UITableViewScrollPositionTop
-                                animated:NO];
+  // Anchoring |position| as the starting point calculate the visible rect area,
+  // based on screen size.
+  CGRect visibleRect = [self.tableView rectForRowAtIndexPath:path];
+  visibleRect =
+      CGRectMake(visibleRect.origin.x, visibleRect.origin.y,
+                 visibleRect.size.width, self.tableView.frame.size.height);
+  [self.tableView scrollRectToVisible:visibleRect animated:NO];
 }
 
 #pragma mark - UITableViewDataSource