Enable VAAPI accelerated decode on Linux

content/content_gpu.gypi

 # 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.
 
 {
   'dependencies': [
     '../base/base.gyp:base',
     '../gpu/gpu.gyp:command_buffer_traits',
     '../gpu/gpu.gyp:gpu',
     '../gpu/gpu.gyp:gpu_ipc_service',
@@ skipping 27 matching lines @@
         # ANGLE libs picked up from ui/gl
         '<(angle_path)/src',
         '<(DEPTH)/third_party/wtl/include',
       ],
       'link_settings': {
         'libraries': [
           '-lsetupapi.lib',
         ],
       },
     }],
-    ['target_arch!="arm" and chromeos == 1', {
+    ['target_arch!="arm" and (chromeos == 1 or OS == "linux")', {
       'include_dirs': [
         '<(DEPTH)/third_party/libva',
       ],
     }],
   ],
 }