Introduce TabRestoreServiceClient and //chrome implementation.

chrome/browser/sessions/session_service.cc

Index: chrome/browser/sessions/session_service.cc
diff --git a/chrome/browser/sessions/session_service.cc b/chrome/browser/sessions/session_service.cc
index 1e241d68f110fdc622e48b087ef43c4789b9ec2b..5cec38511fe718bc817d8997c88deba7a260c484 100644
--- a/chrome/browser/sessions/session_service.cc
+++ b/chrome/browser/sessions/session_service.cc
@@ -497,7 +497,7 @@ void SessionService::SetLastActiveTime(const SessionID& window_id,
 }
 
 base::CancelableTaskTracker::TaskId SessionService::GetLastSession(
-    const SessionCallback& callback,
+    const sessions::GotLastSessionCallback& callback,
     base::CancelableTaskTracker* tracker) {
   // OnGotSessionCommands maps the SessionCommands to browser state, then run
   // the callback.
@@ -695,7 +695,7 @@ void SessionService::OnBrowserSetLastActive(Browser* browser) {
 }
 
 void SessionService::OnGotSessionCommands(
-    const SessionCallback& callback,
+    const sessions::GotLastSessionCallback& callback,
     ScopedVector<sessions::SessionCommand> commands) {
   ScopedVector<sessions::SessionWindow> valid_windows;
   SessionID::id_type active_window_id = 0;