Make sure vp9 actually gets excluded in gn as well.

webrtc/modules/video_coding/BUILD.gn

 # Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("../../build/webrtc.gni")
 
@@ skipping 261 matching lines @@
     "../..:webrtc_common",
     "../../common_video",
     "../../system_wrappers",
   ]
   if (rtc_build_libvpx) {
     deps += [ rtc_libvpx_dir ]
   }
 }
 
 rtc_static_library("webrtc_vp9") {
-  sources = [
-    "codecs/vp9/include/vp9.h",
-    "codecs/vp9/screenshare_layers.cc",
-    "codecs/vp9/screenshare_layers.h",
-    "codecs/vp9/vp9_frame_buffer_pool.cc",
-    "codecs/vp9/vp9_frame_buffer_pool.h",
-    "codecs/vp9/vp9_impl.cc",
-    "codecs/vp9/vp9_impl.h",
-  ]
+  if (rtc_libvpx_build_vp9) {
+    sources = [
+      "codecs/vp9/include/vp9.h",
+      "codecs/vp9/screenshare_layers.cc",
+      "codecs/vp9/screenshare_layers.h",
+      "codecs/vp9/vp9_frame_buffer_pool.cc",
+      "codecs/vp9/vp9_frame_buffer_pool.h",
+      "codecs/vp9/vp9_impl.cc",
+      "codecs/vp9/vp9_impl.h",
+    ]
+  } else {
+    sources = [
+      "codecs/vp9/vp9_noop.cc",
+    ]
+  }
 
   if (is_clang) {
     # Suppress warnings from Chrome's Clang plugins.
     # See http://code.google.com/p/webrtc/issues/detail?id=163 for details.
     suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
   }
 
   deps = [
     ":video_coding_utility",
     "../../common_video",
@@ skipping 23 matching lines @@
       # Suppress warnings from Chrome's Clang plugins.
       # See http://code.google.com/p/webrtc/issues/detail?id=163 for details.
       suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
     }
 
     deps = [
       "../../test:test_support",
     ]
   }
 }