Convert SessionService to use new CancelableTaskTracker

chrome/browser/sessions/session_backend.h

Index: chrome/browser/sessions/session_backend.h
diff --git a/chrome/browser/sessions/session_backend.h b/chrome/browser/sessions/session_backend.h
index 6ae8fbe34cb44aff92505af33328f652f7ad2a62..e7d5c5b13f56cadffa77b706183b9a71846e20fa 100644
--- a/chrome/browser/sessions/session_backend.h
+++ b/chrome/browser/sessions/session_backend.h
@@ -11,6 +11,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/sessions/base_session_service.h"
 #include "chrome/browser/sessions/session_command.h"
+#include "chrome/common/cancelable_task_tracker.h"
 
 namespace net {
 class FileStream;
@@ -65,7 +66,8 @@ class SessionBackend : public base::RefCountedThreadSafe<SessionBackend> {
   // Invoked from the service to read the commands that make up the last
   // session, invokes ReadLastSessionCommandsImpl to do the work.
   void ReadLastSessionCommands(
-      scoped_refptr<BaseSessionService::InternalGetCommandsRequest> request);
+      const CancelableTaskTracker::IsCanceledCallback& is_canceled,
+      const BaseSessionService::InternalGetCommandsCallback& callback);
 
   // Reads the commands from the last file.
   //
@@ -81,11 +83,6 @@ class SessionBackend : public base::RefCountedThreadSafe<SessionBackend> {
   // browsers are running.
   void MoveCurrentSessionToLastSession();
 
-  // Invoked from the service to read the commands that make up the current
-  // session, invokes ReadCurrentSessionCommandsImpl to do the work.
-  void ReadCurrentSessionCommands(
-      scoped_refptr<BaseSessionService::InternalGetCommandsRequest> request);
-
   // Reads the commands from the current file.
   //
   // On success, the read commands are added to commands. It is up to the