Fix V4L2 device failed to create on veyron board

media/gpu/BUILD.gn

 # Copyright 2016 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.
 
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//media/gpu/args.gni")
 import("//media/media_options.gni")
 import("//testing/test.gni")
 
@@ skipping 108 matching lines @@
       "-s",
       stubs_filename_root,
       "-p",
       "media/gpu",
     ]
 
     args += rebase_path(sources, root_build_dir)
   }
 }
 
+config("gpu_config") {
+  defines = []
+  if (is_chromeos && use_v4lplugin) {
+    defines += [ "USE_LIBV4L2" ]
+  }
+}
+
 component("gpu") {
   output_name = "media_gpu"
 
   # Only local test code, GPU-related IPC code in the media layer, and
   # media-related content code should access //media/gpu.
   visibility = [
     "//content/gpu:*",
     "//content/public/gpu:*",
     "//content/renderer:*",
     "//media/gpu/ipc/*",
@@ skipping 21 matching lines @@
     "//ui/gfx/geometry",
   ]
   deps = [
     "//ui/display/types",
     "//ui/gl",
     "//ui/platform_window",
   ]
   libs = []
   ldflags = []
 
+  all_dependent_configs = [ ":gpu_config" ]

[wuchengli, 2016/05/05 14:44:05]

FYI. All targets that transitively depend on the current one will get
gpu_config.

https://chromium.googlesource.com/chromium/src/+/master/tools/gn/docs/quick_s...

[xhwang, 2016/05/05 16:59:13]

Will public_configs work for your use case? We try to avoid using
all_dependent_configs as much as possible.

[kcwu, 2016/05/05 17:17:12]

content/common doesn't depend on media/gpu directly.
Should I add deps to content/common just for getting macro defined?

+
   if (is_mac) {
     sources += [
                  "vt_mac.h",
                  "vt_video_decode_accelerator_mac.cc",
                  "vt_video_decode_accelerator_mac.h",
                  "vt_video_encode_accelerator_mac.cc",
                  "vt_video_encode_accelerator_mac.h",
                ] + get_target_outputs(":libvt_generate_stubs")
     deps += [ ":libvt_generate_stubs" ]
     lib_dirs = [ "$mac_sdk_path/usr/lib" ]
@@ skipping 48 matching lines @@
       "vp8_decoder.cc",
       "vp8_decoder.h",
       "vp8_picture.cc",
       "vp8_picture.h",
       "vp9_decoder.cc",
       "vp9_decoder.h",
       "vp9_picture.cc",
       "vp9_picture.h",
     ]
     if (use_v4lplugin) {
-      defines += [ "USE_LIBV4L2" ]

[wuchengli, 2016/05/05 14:44:05]

FYI. all_dependent_configs applies the config to the target itself. So we don't
need this.

https://chromium.googlesource.com/chromium/src/+/master/tools/gn/docs/quick_s...

       sources += get_target_outputs(":libv4l2_generate_stubs")
       deps += [ ":libv4l2_generate_stubs" ]
     }
     if (use_v4l2_codec) {
       defines += [ "USE_V4L2_CODEC" ]
       deps += [ "//third_party/libyuv" ]
       sources += [
         "generic_v4l2_device.cc",
         "generic_v4l2_device.h",
         "v4l2_device.cc",
@@ skipping 180 matching lines @@
       "video_encode_accelerator_unittest.cc",
     ]
     if (use_x11) {
       deps += [ "//ui/gfx/x" ]
     }
     if (use_ozone) {
       deps += [ "//ui/ozone" ]
     }
   }
 }