[ios] Uses header dynamic height on RecentTabs iOS11

Re-introduces dynamic header height on Recent Tabs for iOS11.
Originally this was removed because of an iOS10 bug, but
there's no need to stop supporting dynamic height on iOS11.

Bug: 862744
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I17ec0f4b2257b23c24d8ed3e285efce023e3e141
Reviewed-on: https://chromium-review.googlesource.com/1142697
Commit-Queue: Sergio Collazos <sczs@chromium.org>
Reviewed-by: Kurt Horimoto <kkhorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576298}

ios/chrome/browser/ui/recent_tabs/recent_tabs_table_view_controller.mm

@@ -157,6 +157,8 @@ const int kRecentlyClosedTabsSectionIndex = 0;
   [self.tableView setDelegate:self];
   self.tableView.cellLayoutMarginsFollowReadableWidth = NO;
   self.tableView.estimatedRowHeight = kEstimatedRowHeight;
+  if (@available(iOS 11.0, *))
+    self.tableView.estimatedSectionHeaderHeight = kEstimatedRowHeight;
   self.tableView.rowHeight = UITableViewAutomaticDimension;
   self.tableView.sectionFooterHeight = 0.0;
   self.title = l10n_util::GetNSString(IDS_IOS_CONTENT_SUGGESTIONS_RECENT_TABS);
@@ -640,15 +642,19 @@ const int kRecentlyClosedTabsSectionIndex = 0;
 - (CGFloat)tableView:(UITableView*)tableView
     heightForHeaderInSection:(NSInteger)section {
   DCHECK_EQ(tableView, self.tableView);
-  NSInteger sectionIdentifier =
-      [self.tableViewModel sectionIdentifierForSection:section];
-  switch (sectionIdentifier) {
-    case SectionIdentifierRecentlyClosedTabs:
-    case SectionIdentifierOtherDevices:
-      return kSingleLineSectionHeaderHeight;
-    default:
-      // All remote session sections.
-      return kDoubleLineSectionHeaderHeight;
+  if (@available(iOS 11, *)) {
+    return UITableViewAutomaticDimension;
+  } else {
+    NSInteger sectionIdentifier =
+        [self.tableViewModel sectionIdentifierForSection:section];
+    switch (sectionIdentifier) {
+      case SectionIdentifierRecentlyClosedTabs:
+      case SectionIdentifierOtherDevices:
+        return kSingleLineSectionHeaderHeight;
+      default:
+        // All remote session sections.
+        return kDoubleLineSectionHeaderHeight;
+    }
   }
 }