Add PlatformWindow/Event related code for Ozone X11.

media/ozone/media_ozone_platform.cc

Index: media/ozone/media_ozone_platform.cc
diff --git a/media/ozone/media_ozone_platform.cc b/media/ozone/media_ozone_platform.cc
index f17d827b1e6fdfbea39640b3e029594dd5e478e6..70a3fd8ae4ece184084206756d8c2246ec6df1d2 100644
--- a/media/ozone/media_ozone_platform.cc
+++ b/media/ozone/media_ozone_platform.cc
@@ -57,6 +57,10 @@ MediaOzonePlatform* CreateMediaOzonePlatformHeadless() {
   return new MediaOzonePlatformStub;
 }
 
+MediaOzonePlatform* CreateMediaOzonePlatformX11() {
+  return new MediaOzonePlatformStub;
+}
+
 MediaOzonePlatform::MediaOzonePlatform() {
   CHECK(!instance_) << "There should only be a single MediaOzonePlatform.";
   instance_ = this;