Fix V4L2VideoEncodeAccelerator is not enabled in GN build

USE_V4L2_CODEC is needed by GpuVideoEncodeAccelerator.

BUG=541408
TEST=check Media.RTCVideoEncoderInitEncodeSuccess histogram

Review-Url: https://codereview.chromium.org/2146463002
Cr-Commit-Position: refs/heads/master@{#405101}

media/gpu/BUILD.gn

@@ -131,6 +131,9 @@ config("gpu_config") {
   if (is_chromeos && use_v4lplugin) {
     defines += [ "USE_LIBV4L2" ]
   }
+  if (is_chromeos && use_v4l2_codec) {
+    defines += [ "USE_V4L2_CODEC" ]
+  }
 }
 
 component("gpu") {
@@ -257,7 +260,6 @@ component("gpu") {
       deps += [ ":libv4l2_generate_stubs" ]
     }
     if (use_v4l2_codec) {
-      defines += [ "USE_V4L2_CODEC" ]
       deps += [ "//third_party/libyuv" ]
       sources += [
         "generic_v4l2_device.cc",

media/gpu/ipc/service/BUILD.gn

@@ -38,6 +38,8 @@ source_set("service") {
     "//third_party/mesa:mesa_headers",
   ]
 
+  configs += [ "//media/gpu:gpu_config" ]
+
   if (is_chromeos && current_cpu != "arm") {
     configs += [ "//third_party/libva:libva_config" ]
   }