Add BUILD.gn files for chromecast/media

media/base/BUILD.gn

Index: media/base/BUILD.gn
diff --git a/media/base/BUILD.gn b/media/base/BUILD.gn
index 861fb6783e338047b1e4ce81df885e13feeb7ac7..1f05d4467dcf2e8ce830e2c2e2c0a77faf9a4085 100644
--- a/media/base/BUILD.gn
+++ b/media/base/BUILD.gn
@@ -4,6 +4,7 @@
 
 import("//build/config/android/config.gni")
 import("//build/config/arm.gni")
+import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//build/config/linux/pkg_config.gni")
 import("//media/media_options.gni")
@@ -241,9 +242,7 @@ source_set("base") {
     sources += [ "user_input_monitor_mac.cc" ]
 
     # Required by video_frame.cc.
-    libs = [
-      "CoreVideo.framework"
-    ]
+    libs = [ "CoreVideo.framework" ]
   } else if (is_win) {
     sources += [ "user_input_monitor_win.cc" ]
   } else {