Dispose of webgl resources properly

Fixes #3889

src/common/Lifecycle.ts

@@ -50,6 +50,13 @@ export abstract class Disposable implements IDisposable {
   }
 }
 
+/**
+ * Wrap a function in a disposable.
+ */
+export function toDisposable(f: () => void): IDisposable {
+  return { dispose: f };
+}
+
 /**
  * Dispose of all disposables in an array and set its length to 0.
  */