Add more targets to "gn check"

device/serial/BUILD.gn

Index: device/serial/BUILD.gn
diff --git a/device/serial/BUILD.gn b/device/serial/BUILD.gn
index 138260486ca2f0a70c3d2061b8b995c6e4dc1d9d..099b7ade2aacd13e20f4982e28d2eea3d9f7e91f 100644
--- a/device/serial/BUILD.gn
+++ b/device/serial/BUILD.gn
@@ -43,12 +43,18 @@ static_library("serial") {
 
   public_deps = [
     ":serial_mojo",
+    "//base",
+  ]
+  deps = [
+    "//third_party/mojo/src/mojo/public/cpp/system",
   ]
-  deps = []
 
   if (is_linux) {
     deps += [ "//device/udev_linux" ]
   }
+  if (is_chromeos) {
+    deps += [ "//chromeos" ]
+  }
 }
 
 # GYP version: device/serial/serial.gyp:device_serial_test_util