Don't create always rejecting promises for timeout

Summary:
Our existing `timeout` implementation was always throwing an exception, due to sleeping and then throw an exception, which is than handled but ignored by `Promise.race`.

This implementation has a few problems

1. Because it always throws, having a debugger session with 'break on caught exceptions' will pause on every usage of timeout (rather than just the ones that actually timeout). This makes this way of debugging a bit useless.
2. Throwing exceptions is in principle an expensive process (due to the stack trace generation)
3. Not cancelling the timeout used by sleep is a bit of a waste as well

Reviewed By: lawrencelomax

Differential Revision: D33982717

fbshipit-source-id: d739c02112e1c1bc4cd691af852371d08a99abc6

desktop/flipper-common/src/utils/timeout.tsx

@@ -7,18 +7,21 @@
  * @format
  */
 
-import {sleep} from './sleep';
-
 export function timeout<T>(
   ms: number,
   promise: Promise<T>,
   timeoutMessage?: string,
 ): Promise<T> {
-  // Create a promise that rejects in <ms> milliseconds
-  const timeout = sleep(ms).then(() => {
-    throw new Error(timeoutMessage || `Timed out in ${ms} ms.`);
-  });
+  return new Promise((resolve, reject) => {
+    const timeoutHandle = setTimeout(() => {
+      reject(new Error(timeoutMessage || `Timed out in ${ms} ms.`));
+    }, ms);
 
-  // Returns a race between our timeout and the passed in promise
-  return Promise.race([promise, timeout]);
+    promise
+      .then(resolve)
+      .finally(() => {
+        clearTimeout(timeoutHandle);
+      })
+      .catch(reject);
+  });
 }