Fix V4L2VideoEncodeAccelerator is not enabled in GN build

media/gpu/ipc/service/BUILD.gn

Index: media/gpu/ipc/service/BUILD.gn
diff --git a/media/gpu/ipc/service/BUILD.gn b/media/gpu/ipc/service/BUILD.gn
index 17acc263494c5a5417010568cd1283b006be910a..f49d6527d993ff67d7e2d5d6e7c94375b1adb8a6 100644
--- a/media/gpu/ipc/service/BUILD.gn
+++ b/media/gpu/ipc/service/BUILD.gn
@@ -38,6 +38,8 @@ source_set("service") {
     "//third_party/mesa:mesa_headers",
   ]
 
+  public_configs = [ "//media/gpu:gpu_config" ]

[wuchengli, 2016/07/12 11:39:51]

s/public_configs/configs/. We don't need to propagate this to the dependents of
this target.

Please also help change public_configs to configs in
media/gpu/ipc/client/BUILD.gn.

[wuchengli, 2016/07/12 15:00:55]

I found why media/gpu/ipc/client/BUILD.gn used public_configs.
bpf_gpu_policy_linux.cc needs USE_LIBV4L2 and it depends on
media/gpu/ipc/client. No need to change media/gpu/ipc/client/BUILD.gn.

[henryhsu, 2016/07/13 03:29:59]

Done.

+
   if (is_chromeos && current_cpu != "arm") {
     configs += [ "//third_party/libva:libva_config" ]
   }