[ios clean] Toolbar displays total number of tabs.

ios/clean/chrome/browser/ui/toolbar/toolbar_mediator.mm

Index: ios/clean/chrome/browser/ui/toolbar/toolbar_mediator.mm
diff --git a/ios/clean/chrome/browser/ui/toolbar/toolbar_mediator.mm b/ios/clean/chrome/browser/ui/toolbar/toolbar_mediator.mm
index e08207600277c0f8c59b857d18d827b516893058..dfc05121b7939309b9bd5043c5580b8cd50cea54 100644
--- a/ios/clean/chrome/browser/ui/toolbar/toolbar_mediator.mm
+++ b/ios/clean/chrome/browser/ui/toolbar/toolbar_mediator.mm
@@ -5,7 +5,10 @@
 #import "ios/clean/chrome/browser/ui/toolbar/toolbar_mediator.h"
 
 #include "base/memory/ptr_util.h"
+#include "base/scoped_observer.h"
 #include "base/strings/sys_string_conversions.h"
+#import "ios/chrome/browser/web_state_list/web_state_list.h"
+#import "ios/chrome/browser/web_state_list/web_state_list_observer_bridge.h"
 #import "ios/clean/chrome/browser/ui/toolbar/toolbar_consumer.h"
 #import "ios/web/public/navigation_manager.h"
 #include "ios/web/public/web_state/web_state.h"
@@ -15,19 +18,29 @@
 #error "This file requires ARC support."
 #endif
 
-@interface ToolbarMediator ()<CRWWebStateObserver>
+@interface ToolbarMediator ()<CRWWebStateObserver, WebStateListObserving>
 @end
 
 @implementation ToolbarMediator {
   std::unique_ptr<web::WebStateObserverBridge> _webStateObserver;
+  std::unique_ptr<WebStateListObserverBridge> _webStateListObserver;
+  std::unique_ptr<ScopedObserver<WebStateList, WebStateListObserverBridge>>
+      _scopedWebStateListObserver;
 }
 
 @synthesize consumer = _consumer;
 @synthesize webState = _webState;
+@synthesize webStateList = _webStateList;
 
 - (void)dealloc {
+  [self disconnect];
+}
+
+#pragma mark - Public
+
+- (void)disconnect {
+  self.webStateList = nullptr;
   _webStateObserver.reset();
-  _webState = nullptr;
 }
 
 #pragma mark - CRWWebStateObserver
@@ -58,6 +71,20 @@
   [self.consumer setTabStripVisible:visible];
 }
 
+#pragma mark - WebStateListObserver
+
+- (void)webStateList:(WebStateList*)webStateList
+    didInsertWebState:(web::WebState*)webState
+              atIndex:(int)index {
+  [self.consumer setTabCount:_webStateList->count()];
+}
+
+- (void)webStateList:(WebStateList*)webStateList
+    didDetachWebState:(web::WebState*)webState
+              atIndex:(int)index {
+  [self.consumer setTabCount:_webStateList->count()];
+}
+
 #pragma mark - Setters
 
 - (void)setWebState:(web::WebState*)webState {
@@ -74,6 +101,24 @@
   if (self.webState) {
     [self updateConsumer];
   }
+  if (self.webStateList) {
+    [self.consumer setTabCount:_webStateList->count()];
+  }
+}
+
+- (void)setWebStateList:(WebStateList*)webStateList {
+  // TODO(crbug.com/727427):Add support for DCHECK(webStateList).
+  _webStateList = webStateList;
+  _webStateListObserver = base::MakeUnique<WebStateListObserverBridge>(self);
+  _scopedWebStateListObserver = base::MakeUnique<
+      ScopedObserver<WebStateList, WebStateListObserverBridge>>(
+      _webStateListObserver.get());
+  if (_webStateList) {
+    _scopedWebStateListObserver->Add(_webStateList);
+    if (self.consumer) {
+      [self.consumer setTabCount:_webStateList->count()];
+    }
+  }
 }
 
 #pragma mark - Helper methods