Move mouse wheel fix out of patch

packages/vscode/src/fill/mouseEvent.ts

@@ -0,0 +1,19 @@
+import * as mouse from "vs/base/browser/mouseEvent";
+
+/**
+ * Fix the wheel event for Firefox.
+ */
+class StandardWheelEvent extends mouse.StandardWheelEvent {
+
+	public constructor(event: mouse.IMouseWheelEvent | null) {
+		super(
+			event,
+			(-(event as any as MouseWheelEvent).deltaX || 0) / 3, // tslint:disable-line no-any
+			(-(event as any as MouseWheelEvent).deltaY || 0) / 3, // tslint:disable-line no-any
+		);
+	}
+
+}
+
+const target = mouse as typeof mouse;
+target.StandardWheelEvent = StandardWheelEvent;