Add a new SyncedTabDelegate for Android.

chrome/browser/sessions/session_tab_helper.h

 // Copyright (c) 2011 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 CHROME_BROWSER_SESSIONS_SESSION_TAB_HELPER_H_
 #define CHROME_BROWSER_SESSIONS_SESSION_TAB_HELPER_H_
 
 #include "base/basictypes.h"
 #include "chrome/browser/sessions/session_id.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
 
 // This class keeps the extension API's windowID up-to-date with the current
 // window of the tab.
 class SessionTabHelper : public content::WebContentsObserver,
                          public content::WebContentsUserData<SessionTabHelper> {
  public:
   virtual ~SessionTabHelper();
 
   // Returns the identifier used by session restore for this tab.
   const SessionID& session_id() const { return session_id_; }
+  void SetSessionId(const SessionID& id);

[sky, 2013/05/21 04:53:01]

Why do you need to dynamically change the session id? Doing so could cause all
sorts of problems and I don't want to expose this.

[shashi, 2013/05/21 05:16:35]

Sorry my intent is not to dynamically change but to set it at instantiation
time. Now I realize it can be potentially misused, Perhaps a better way would be
to add a new static method:

static public void CreateForWebContents(WebContents * webcontents, const
SessionId& id) {
  CreateForWebContents(webcontents);
   FromWebContents(webcontents)->SetSessionId(id);
}
 
the new method SetSessionID is then private. This way we never expose this
method.

Background:
On Android we can have tab id assigned to tab even before web contents have been
created and all our tabs do not have web contents, (we do this to reduce memory
footprint of app, otherwise Chrome will be killed by operating system.) This
means if a user switches to a tab which was not in memory the SessionID
associated with it can change, since a lot of places use
SessionTabHelper::FromWebContents()->session_id for getting the tab id.

A lot of places in Chrome use SessionTabHelper to get SessionID.

On 2013/05/21 04:53:01, sky wrote:

[sky, 2013/05/21 15:00:44]

Is it possible to lookup the id you want to assign in SessionTabHelper's
constructor?

[shashi, 2013/05/21 16:01:13]

The id I want to assign is TabAndroid id, I don't think I can look it up in the
constructor, unless I pass the pointer to TabAndroid here.
On 2013/05/21 15:00:44, sky wrote:

[shashi, 2013/05/21 23:11:21]

Done.

 
   // Identifier of the window the tab is in.
   void SetWindowID(const SessionID& id);
   const SessionID& window_id() const { return window_id_; }
 
   // content::WebContentsObserver:
   virtual void RenderViewCreated(
       content::RenderViewHost* render_view_host) OVERRIDE;
   virtual void UserAgentOverrideSet(const std::string& user_agent) OVERRIDE;
 
  private:
   explicit SessionTabHelper(content::WebContents* contents);
   friend class content::WebContentsUserData<SessionTabHelper>;
 
   // Unique identifier of the tab for session restore. This id is only unique
   // within the current session, and is not guaranteed to be unique across
   // sessions.
-  const SessionID session_id_;
+  SessionID session_id_;
 
   // Unique identifier of the window the tab is in.
   SessionID window_id_;
 
   DISALLOW_COPY_AND_ASSIGN(SessionTabHelper);
 };
 
 #endif  // CHROME_BROWSER_SESSIONS_SESSION_TAB_HELPER_H_