[sync] WebContentsObserver based sessions notifications

ios/chrome/browser/sync/ios_chrome_synced_tab_delegate.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef IOS_CHROME_BROWSER_SYNC_IOS_CHROME_SYNCED_TAB_DELEGATE_H_
 #define IOS_CHROME_BROWSER_SYNC_IOS_CHROME_SYNCED_TAB_DELEGATE_H_
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "components/sessions/core/session_id.h"
 #include "components/sync_sessions/synced_tab_delegate.h"
 #include "ios/web/public/web_state/web_state_user_data.h"
 
 class IOSChromeSyncedTabDelegate
     : public sync_sessions::SyncedTabDelegate,
       public web::WebStateUserData<IOSChromeSyncedTabDelegate> {
  public:
   ~IOSChromeSyncedTabDelegate() override;
 
   // SyncedTabDelegate:
   SessionID::id_type GetWindowId() const override;
   SessionID::id_type GetSessionId() const override;
   bool IsBeingDestroyed() const override;
+  SessionID::id_type GetSourceTabID() const override;
   std::string GetExtensionAppId() const override;
   bool IsInitialBlankNavigation() const override;
   int GetCurrentEntryIndex() const override;
   int GetEntryCount() const override;
   GURL GetVirtualURLAtIndex(int i) const override;
   GURL GetFaviconURLAtIndex(int i) const override;
   ui::PageTransition GetTransitionAtIndex(int i) const override;
   void GetSerializedNavigationAtIndex(
       int i,
       sessions::SerializedNavigationEntry* serialized_entry) const override;
   bool ProfileIsSupervised() const override;
   const std::vector<std::unique_ptr<const sessions::SerializedNavigationEntry>>*
   GetBlockedNavigations() const override;
   bool IsPlaceholderTab() const override;
   int GetSyncId() const override;
   void SetSyncId(int sync_id) override;
   bool ShouldSync(sync_sessions::SyncSessionsClient* sessions_client) override;
 
  private:
   explicit IOSChromeSyncedTabDelegate(web::WebState* web_state);
   friend class web::WebStateUserData<IOSChromeSyncedTabDelegate>;
 
   web::WebState* web_state_;
   int sync_session_id_;
 
   DISALLOW_COPY_AND_ASSIGN(IOSChromeSyncedTabDelegate);
 };
 
 #endif  // IOS_CHROME_BROWSER_SYNC_IOS_CHROME_SYNCED_TAB_DELEGATE_H_