session_manager: Tracks user sessions

components/session_manager/core/BUILD.gn

 # Copyright 2014 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.
 
 component("core") {
   sources = [
     "session_manager.cc",
     "session_manager.h",
   ]
   deps = [
     "//base",
     "//components/session_manager:base",
+    "//components/signin/core/account_id",
+    "//components/user_manager",
+    "//skia",
   ]
   defines = [ "SESSION_IMPLEMENTATION" ]
 }