Implement stdweb backend for web platform

src/platform_impl/web/stdweb/mod.rs

@@ -1,6 +1,21 @@
-#[cfg(feature = "stdweb")]
-impl WindowExtStdweb for RootWindow {
+mod canvas;
+mod event;
+mod timeout;
+
+pub use self::canvas::Canvas;
+pub use self::timeout::Timeout;
+
+use crate::platform::web::WindowExtStdweb;
+use crate::window::Window;
+
+use stdweb::web::html_element::CanvasElement;
+
+pub fn throw(msg: &str) {
+    js! { throw @{msg} }
+}
+
+impl WindowExtStdweb for Window {
     fn canvas(&self) -> CanvasElement {
-        self.window.canvas.clone()
+        self.window.canvas().raw().clone()
     }
 }