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

chrome/browser/sessions/session_id.cc

-// 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.
-
-#include "chrome/browser/sessions/session_id.h"
-
-#include "chrome/browser/sessions/session_tab_helper.h"
-
-static SessionID::id_type next_id = 1;
-
-SessionID::SessionID() {
-  id_ = next_id++;
-}
-
-SessionID::id_type SessionID::IdForTab(const content::WebContents* tab) {
-  const SessionTabHelper* session_tab_helper =
-      tab ? SessionTabHelper::FromWebContents(tab) : NULL;
-  return session_tab_helper ? session_tab_helper->session_id().id() : -1;
-}
-
-SessionID::id_type SessionID::IdForWindowContainingTab(
-    const content::WebContents* tab) {
-  const SessionTabHelper* session_tab_helper =
-      tab ? SessionTabHelper::FromWebContents(tab) : NULL;
-  return session_tab_helper ? session_tab_helper->window_id().id() : -1;
-}