Remove Compositor window generic

And update `glyphon` and `window_clipboard`

futures/src/maybe.rs

@@ -0,0 +1,35 @@
+#[cfg(not(target_arch = "wasm32"))]
+mod platform {
+    /// An extension trait that enforces `Send` only on native platforms.
+    ///
+    /// Useful to write cross-platform async code!
+    pub trait MaybeSend: Send {}
+
+    impl<T> MaybeSend for T where T: Send {}
+
+    /// An extension trait that enforces `Sync` only on native platforms.
+    ///
+    /// Useful to write cross-platform async code!
+    pub trait MaybeSync: Sync {}
+
+    impl<T> MaybeSync for T where T: Sync {}
+}
+
+#[cfg(target_arch = "wasm32")]
+mod platform {
+    /// An extension trait that enforces `Send` only on native platforms.
+    ///
+    /// Useful to write cross-platform async code!
+    pub trait MaybeSend {}
+
+    impl<T> MaybeSend for T {}
+
+    /// An extension trait that enforces `Send` only on native platforms.
+    ///
+    /// Useful to write cross-platform async code!
+    pub trait MaybeSync {}
+
+    impl<T> MaybeSync for T {}
+}
+
+pub use platform::{MaybeSend, MaybeSync};