spawn a task for cef async browser creation to kick the main loop awake

without this, the initial url loading message will never be sent to the
constellation, preventing the engine from ever doing anything

ports/cef/browser.rs

@@ -10,6 +10,7 @@ use interfaces::{cef_browser_t, cef_browser_host_t, cef_client_t, cef_frame_t};
 use interfaces::{cef_request_context_t};
 use servo::Browser;
 use types::{cef_browser_settings_t, cef_string_t, cef_window_info_t, cef_window_handle_t};
+use util::task::spawn_named;
 use window;
 use wrappers::CefWrap;
 
@@ -297,6 +298,9 @@ cef_static_method_impls! {
         let _browser_settings: &cef_browser_settings_t = _browser_settings;
         let _request_context: CefRequestContext = _request_context;
         browser_host_create(window_info, client, url, false);
+        spawn_named("async_browser_creation".to_owned(), move || {
+            window::app_wakeup();
+        });
         1i32
     }}
     fn cef_browser_host_create_browser_sync(window_info: *const cef_window_info_t,