Move session_id.{cc,h} from chrome/browser/sessions to components/sessions

chrome/browser/sessions/session_id.h

-// Copyright (c) 2012 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_ID_H_
-#define CHROME_BROWSER_SESSIONS_SESSION_ID_H_
-
-#include "base/basictypes.h"
-
-namespace content {
-class WebContents;
-}
-
-// Uniquely identifies a tab or window for the duration of a session.
-class SessionID {
- public:
-  typedef int32 id_type;
-
-  SessionID();
-  ~SessionID() {}
-
-  // If the specified WebContents has a SessionTabHelper (probably because it
-  // was used as the contents of a tab), returns a tab id. This value is
-  // immutable for a given tab. It will be unique across Chrome within the
-  // current session, but may be re-used across sessions. Returns -1
-  // for a NULL WebContents or if the WebContents has no SessionTabHelper.
-  static id_type IdForTab(const content::WebContents* tab);
-
-  // If the specified WebContents has a SessionTabHelper (probably because it
-  // was used as the contents of a tab), and has ever been attached to a Browser
-  // window, returns Browser::session_id().id() for that Browser. If the tab is
-  // being dragged between Browser windows, returns the old window's id value.
-  // If the WebContents has a SessionTabHelper but has never been attached to a
-  // Browser window, returns an id value that is different from that of any
-  // Browser. Returns -1 for a NULL WebContents or if the WebContents has no
-  // SessionTabHelper.
-  static id_type IdForWindowContainingTab(const content::WebContents* tab);
-
-  // Returns the underlying id.
-  void set_id(id_type id) { id_ = id; }
-  id_type id() const { return id_; }
-
- private:
-  id_type id_;
-};
-
-#endif  // CHROME_BROWSER_SESSIONS_SESSION_ID_H_