Fix V4L2 device failed to create on veyron board

media/gpu/BUILD.gn

Index: media/gpu/BUILD.gn
diff --git a/media/gpu/BUILD.gn b/media/gpu/BUILD.gn
index 87592d7fada7e593347733bdf753972b2478cd60..6977de1d3a9fe3140dbf2c0a5e68f1b9f1444481 100644
--- a/media/gpu/BUILD.gn
+++ b/media/gpu/BUILD.gn
@@ -126,6 +126,13 @@ if (is_mac) {
   }
 }
 
+config("gpu_config") {
+  defines = []
+  if (is_chromeos && use_v4lplugin) {
+    defines += [ "USE_LIBV4L2" ]
+  }
+}
+
 component("gpu") {
   output_name = "media_gpu"
 
@@ -167,6 +174,8 @@ component("gpu") {
   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",
@@ -235,7 +244,6 @@ component("gpu") {
       "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" ]
     }