remove and add unused code

src/vs/base/common/lifecycle.ts

@@ -15,6 +15,11 @@ export interface IDisposable {
 	dispose(): void;
 }
 
+export function isDisposable<E extends object>(thing: E): thing is E & IDisposable {
+	return typeof (<IDisposable><any>thing).dispose === 'function'
+		&& (<IDisposable><any>thing).dispose.length === 0;
+}
+
 export function dispose<T extends IDisposable>(disposable: T): T;
 export function dispose<T extends IDisposable>(...disposables: T[]): T[];
 export function dispose<T extends IDisposable>(disposables: T[]): T[];
@@ -68,22 +73,6 @@ export abstract class Disposable implements IDisposable {
 	}
 }
 
-export class OneDisposable implements IDisposable {
-
-	private _value: IDisposable;
-
-	set value(value: IDisposable) {
-		if (this._value) {
-			this._value.dispose();
-		}
-		this._value = value;
-	}
-
-	dispose() {
-		this.value = null;
-	}
-}
-
 export interface IReference<T> extends IDisposable {
 	readonly object: T;
 }