Replace TabModel with WebStateList in GoogleLandingController.

ios/chrome/browser/ui/ntp/new_tab_page_header_view.mm

Index: ios/chrome/browser/ui/ntp/new_tab_page_header_view.mm
diff --git a/ios/chrome/browser/ui/ntp/new_tab_page_header_view.mm b/ios/chrome/browser/ui/ntp/new_tab_page_header_view.mm
index 46590152472ef374e572197757653b01f1809938..a9a519412da9c7a5afbea8479ae889211ed5c3c9 100644
--- a/ios/chrome/browser/ui/ntp/new_tab_page_header_view.mm
+++ b/ios/chrome/browser/ui/ntp/new_tab_page_header_view.mm
@@ -25,9 +25,8 @@ const CGFloat kMaxConstraintConstantDiff = 5;
 
 }  // namespace
 
-@interface NewTabPageHeaderView ()<TabModelObserver> {
+@interface NewTabPageHeaderView () {
   base::scoped_nsobject<NewTabPageToolbarController> _toolbarController;
-  base::scoped_nsobject<TabModel> _tabModel;
   base::scoped_nsobject<UIImageView> _searchBoxBorder;
   base::scoped_nsobject<UIImageView> _shadow;
 }
@@ -45,7 +44,6 @@ const CGFloat kMaxConstraintConstantDiff = 5;
 }
 
 - (void)dealloc {
-  [_tabModel removeObserver:self];
   [super dealloc];
 }
 
@@ -74,9 +72,6 @@ const CGFloat kMaxConstraintConstantDiff = 5;
       initWithToolbarDelegate:[dataSource toolbarDelegate]
                       focuser:dataSource]);
   _toolbarController.get().readingListModel = [dataSource readingListModel];
-  [_tabModel removeObserver:self];
-  _tabModel.reset([[dataSource tabModel] retain]);
-  [self addTabModelObserver];
 
   UIView* toolbarView = [_toolbarController view];
   CGRect toolbarFrame = self.bounds;
@@ -93,9 +88,8 @@ const CGFloat kMaxConstraintConstantDiff = 5;
   [_toolbarController hideViewsForNewTabPage:YES];
 };
 
-- (void)addTabModelObserver {
-  [_tabModel addObserver:self];
-  [_toolbarController setTabCount:[_tabModel count]];
+- (void)setToolbarTabCount:(int)tabCount {
+  [_toolbarController setTabCount:tabCount];
 }
 
 - (void)addViewsToSearchField:(UIView*)searchField {
@@ -122,11 +116,6 @@ const CGFloat kMaxConstraintConstantDiff = 5;
   [_shadow setAlpha:0];
 }
 
-- (void)tabModelDidChangeTabCount:(TabModel*)model {
-  DCHECK(model == _tabModel);
-  [_toolbarController setTabCount:[_tabModel count]];
-}
-
 - (void)updateSearchField:(UIView*)searchField
          withInitialFrame:(CGRect)initialFrame
        subviewConstraints:(NSArray*)constraints