Revert "Merge from vscode 81d7885dc2e9dc617e1522697a2966bc4025a45d (#5949)" (#5983)

This reverts commit d15a3fcc98.

src/vs/base/node/pfs.ts

@@ -226,7 +226,7 @@ export function readFile(path: string, encoding?: string): Promise<Buffer | stri
 // According to node.js docs (https://nodejs.org/docs/v6.5.0/api/fs.html#fs_fs_writefile_file_data_options_callback)
 // it is not safe to call writeFile() on the same path multiple times without waiting for the callback to return.
 // Therefor we use a Queue on the path that is given to us to sequentialize calls to the same path properly.
-const writeFilePathQueues: Map<string, Queue<void>> = new Map();
+const writeFilePathQueue: { [path: string]: Queue<void> } = Object.create(null);
 
 export function writeFile(path: string, data: string, options?: IWriteFileOptions): Promise<void>;
 export function writeFile(path: string, data: Buffer, options?: IWriteFileOptions): Promise<void>;
@@ -249,20 +249,18 @@ function toQueueKey(path: string): string {
 }
 
 function ensureWriteFileQueue(queueKey: string): Queue<void> {
-	const existingWriteFileQueue = writeFilePathQueues.get(queueKey);
-	if (existingWriteFileQueue) {
-		return existingWriteFileQueue;
+	let writeFileQueue = writeFilePathQueue[queueKey];
+	if (!writeFileQueue) {
+		writeFileQueue = new Queue<void>();
+		writeFilePathQueue[queueKey] = writeFileQueue;
+
+		const onFinish = Event.once(writeFileQueue.onFinished);
+		onFinish(() => {
+			delete writeFilePathQueue[queueKey];
+			writeFileQueue.dispose();
+		});
 	}
 
-	const writeFileQueue = new Queue<void>();
-	writeFilePathQueues.set(queueKey, writeFileQueue);
-
-	const onFinish = Event.once(writeFileQueue.onFinished);
-	onFinish(() => {
-		writeFilePathQueues.delete(queueKey);
-		writeFileQueue.dispose();
-	});
-
 	return writeFileQueue;
 }