Merge from vscode 4d91d96e5e121b38d33508cdef17868bab255eae

src/vs/base/common/event.ts

@@ -440,14 +440,14 @@ class LeakageMonitor {
 			this._warnCountdown = threshold * 0.5;
 
 			// find most frequent listener and print warning
-			let topStack: string;
+			let topStack: string | undefined;
 			let topCount: number = 0;
-			this._stacks.forEach((count, stack) => {
+			for (const [stack, count] of this._stacks) {
 				if (!topStack || topCount < count) {
 					topStack = stack;
 					topCount = count;
 				}
-			});
+			}
 
 			console.warn(`[${this.name}] potential listener LEAK detected, having ${listenerCount} listeners already. MOST frequent listener (${topCount}):`);
 			console.warn(topStack!);