[ios] Extend WebStateListObserver amd WebStateListDelegate APIs.

ios/shared/chrome/browser/tabs/web_state_list_observer_bridge.mm

Index: ios/shared/chrome/browser/tabs/web_state_list_observer_bridge.mm
diff --git a/ios/shared/chrome/browser/tabs/web_state_list_observer_bridge.mm b/ios/shared/chrome/browser/tabs/web_state_list_observer_bridge.mm
index 7539c26baaa03994815c6be9d663f68a9398060e..86e847f6f9f305c8231eceea945c8113a1f0df0a 100644
--- a/ios/shared/chrome/browser/tabs/web_state_list_observer_bridge.mm
+++ b/ios/shared/chrome/browser/tabs/web_state_list_observer_bridge.mm
@@ -58,6 +58,19 @@ void WebStateListObserverBridge::WebStateReplacedAt(
                   atIndex:index];
 }
 
+void WebStateListObserverBridge::WillDetachWebStateAt(
+    WebStateList* web_state_list,
+    web::WebState* web_state,
+    int index) {
+  const SEL selector = @selector(webStateList:willDetachWebState:atIndex:);
+  if (![observer_ respondsToSelector:selector])
+    return;
+
+  [observer_ webStateList:web_state_list
+       willDetachWebState:web_state
+                  atIndex:index];
+}
+
 void WebStateListObserverBridge::WebStateDetachedAt(
     WebStateList* web_state_list,
     web::WebState* web_state,
@@ -71,6 +84,19 @@ void WebStateListObserverBridge::WebStateDetachedAt(
                   atIndex:index];
 }
 
+void WebStateListObserverBridge::WillCloseWebStateAt(
+    WebStateList* web_state_list,
+    web::WebState* web_state,
+    int index) {
+  const SEL selector = @selector(webStateList:willCloseWebState:atIndex:);
+  if (![observer_ respondsToSelector:selector])
+    return;
+
+  [observer_ webStateList:web_state_list
+        willCloseWebState:web_state
+                  atIndex:index];
+}
+
 void WebStateListObserverBridge::WebStateActivatedAt(
     WebStateList* web_state_list,
     web::WebState* old_web_state,