[ios] Added web// public API to let embedder observe loading progress.

ios/web/web_state/web_state_impl.h

Index: ios/web/web_state/web_state_impl.h
diff --git a/ios/web/web_state/web_state_impl.h b/ios/web/web_state/web_state_impl.h
index 7924ae25f537d286ea0efb61e4238d03179403a1..276cca662c11b4721aeb753848535749fb6643dd 100644
--- a/ios/web/web_state/web_state_impl.h
+++ b/ios/web/web_state/web_state_impl.h
@@ -41,6 +41,7 @@ struct FaviconURL;
 struct LoadCommittedDetails;
 class NavigationManager;
 class WebInterstitialImpl;
+class WebStateDelegate;
 class WebStateFacadeDelegate;
 class WebStatePolicyDecider;
 class WebUIIOS;
@@ -216,6 +217,8 @@ class WebStateImpl : public WebState, public NavigationManagerDelegate {
   NSString* GetRequestGroupID();
 
   // WebState:
+  WebStateDelegate* GetDelegate() override;
+  void SetDelegate(WebStateDelegate* delegate) override;
   UIView* GetView() override;
   web::WebViewType GetWebViewType() const override;
   BrowserState* GetBrowserState() const override;
@@ -251,6 +254,9 @@ class WebStateImpl : public WebState, public NavigationManagerDelegate {
   // Called to dismiss the currently-displayed transient content view.
   void ClearTransientContentView();
 
+  // Notifies the delegate that the load progress was updated.
+  void SendChangeLoadProgress(double progress);
+
   // NavigationManagerDelegate:
   void NavigateToPendingEntry() override;
   void LoadURLWithParams(const NavigationManager::WebLoadParams&) override;
@@ -267,6 +273,9 @@ class WebStateImpl : public WebState, public NavigationManagerDelegate {
   void RemovePolicyDecider(WebStatePolicyDecider* decider) override;
 
  private:
+  // Unowned delegate.
+  WebStateDelegate* delegate_;
+
   // Creates a WebUIIOS object for |url| that is owned by the caller. Returns
   // nullptr if |url| does not correspond to a WebUI page.
   WebUIIOS* CreateWebUIIOS(const GURL& url);