[ios] Adds RecentTabsVC TableViewModel support.

Deletes old table view DataSource implementation and creates a TableViewModel instead.
Moves Item/Cell configuration logic from recent_tabs/views/ into the VC.
Some helper methods are being re-used.


Screenshots:
https://drive.google.com/open?id=1n-IYyIffatHC2ok9fnvyIRhqH6rLADuh
https://drive.google.com/open?id=14NuWwnYFncYfijRpjIuy8kQ-EDYuIze6

Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: If997fb74862d135ff68e2b4aafd930d90f13f159
Reviewed-on: https://chromium-review.googlesource.com/954227
Commit-Queue: Sergio Collazos <sczs@chromium.org>
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#542239}

ios/chrome/browser/ui/ntp/recent_tabs/BUILD.gn

@@ -33,6 +33,7 @@ source_set("recent_tabs") {
     "//base",
     "//components/browser_sync",
     "//components/sessions",
+    "//components/strings",
     "//components/sync",
     "//ios/chrome/app/strings",
     "//ios/chrome/app/theme",

ios/chrome/browser/ui/table_view/cells/table_view_text_header_footer_item.mm

@@ -31,6 +31,10 @@ const CGFloat kMargin = 16;
   TableViewTextHeaderFooterView* header =
       base::mac::ObjCCastStrict<TableViewTextHeaderFooterView>(headerFooter);
   header.textLabel.text = self.text;
+  // Set the contentView backgroundColor, not the header's.
+  header.contentView.backgroundColor = [UIColor whiteColor];
+  header.textLabel.font =
+      [UIFont preferredFontForTextStyle:UIFontTextStyleHeadline];
 }
 
 @end
@@ -46,7 +50,6 @@ const CGFloat kMargin = 16;
     // Text Label, set font sizes using dynamic type.
     _textLabel = [[UILabel alloc] init];
     _textLabel.translatesAutoresizingMaskIntoConstraints = NO;
-    _textLabel.font = [UIFont preferredFontForTextStyle:UIFontTextStyleBody];
 
     // Container View.
     UIView* containerView = [[UIView alloc] init];

ios/chrome/browser/ui/table_view/chrome_table_view_controller.mm

@@ -21,6 +21,15 @@
   _tableViewModel = [[TableViewModel alloc] init];
 }
 
+#pragma mark - ViewLifeCycle
+
+- (void)viewDidLoad {
+  [super viewDidLoad];
+  [self.tableView setBackgroundColor:[UIColor whiteColor]];
+  [self.tableView setSeparatorColor:[UIColor grayColor]];
+  [self.tableView setSeparatorInset:UIEdgeInsetsMake(0, 56, 0, 0)];
+}
+
 #pragma mark - UITableViewDataSource
 
 - (UITableViewCell*)tableView:(UITableView*)tableView
@@ -54,7 +63,7 @@
   TableViewHeaderFooterItem* item =
       [self.tableViewModel headerForSection:section];
   if (!item)
-    return [super tableView:self.tableView viewForHeaderInSection:section];
+    return [[UIView alloc] initWithFrame:CGRectZero];
   Class headerFooterClass = [item cellClass];
   NSString* reuseIdentifier = NSStringFromClass(headerFooterClass);
   [self.tableView registerClass:headerFooterClass
@@ -70,7 +79,7 @@
   TableViewHeaderFooterItem* item =
       [self.tableViewModel footerForSection:section];
   if (!item)
-    return [super tableView:self.tableView viewForHeaderInSection:section];
+    return [[UIView alloc] initWithFrame:CGRectZero];
   Class headerFooterClass = [item cellClass];
   NSString* reuseIdentifier = NSStringFromClass(headerFooterClass);
   [self.tableView registerClass:headerFooterClass