Move SessionID, CaptureVisibleTabFunction to WebContents.

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