[iOS] Adjust top/bottom insets of Popup Menu

The bottom insets of the popup menus were wrong because of a rounding
error. This CL adjusts it by rounding at the end of the additions
instead of doing everytime a new element is computed.

Bug: 850516
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: Ic99c3d71e1f7d8a0b47a3e6453242d4a36007e66
Reviewed-on: https://chromium-review.googlesource.com/1174253
Commit-Queue: Stepan Khapugin <stkhapugin@chromium.org>
Reviewed-by: Stepan Khapugin <stkhapugin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582902}

ios/chrome/browser/ui/popup_menu/popup_menu_table_view_controller.mm

@@ -171,14 +171,14 @@ const CGFloat kScrollIndicatorVerticalInsets = 11;
          [self.tableViewModel itemsInSectionWithIdentifier:sectionIdentifier]) {
       CGSize sizeForCell = [item cellSizeForWidth:self.view.bounds.size.width];
       width = MAX(width, ceil(sizeForCell.width));
-      height += ceil(sizeForCell.height);
+      height += sizeForCell.height;
     }
     // Add the separator height (only available the non-final sections).
     height += [self tableView:self.tableView heightForFooterInSection:section];
   }
   height +=
       self.tableView.contentInset.top + self.tableView.contentInset.bottom;
-  return CGSizeMake(width, height);
+  return CGSizeMake(width, ceil(height));
 }
 
 #pragma mark - UITableViewDelegate