Hi, long time user, first time issuer.

I think I found a bug with the Profiler component. When I click on the `Save profile...` button at the top nothing happens and there appears to be no new files in my Downloads folder. I think it might be silently failing and that's why I am not getting any response.  Has anyone else ran into this issue?

Another thing I would like to mention is that I haven't looked through all of the documentation material about the new Profiler. I only read [this introductory blog post](https://reactjs.org/blog/2018/09/10/introducing-the-react-profiler.html), so if this issue is addressed elsewhere I apologize and also request the source to that solution.

Thank you for your time!

**Versions:**
 * `React DevTools 4.0.5`
 * `Firefox: 68.0.2(64-bit)`
 * `Ubuntu: 18.04`

/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow
 */
import escapeStringRegExp from 'escape-string-regexp';
import {meta} from '../../hydration';
import type {HooksTree} from 'react-debug-tools/src/ReactDebugHooks';
export function alphaSortEntries(
  entryA: [string, mixed],
  entryB: [string, mixed],
): number {
  const a = entryA[0];
  const b = entryB[0];
  if ('' + +a === a) {
    if ('' + +b !== b) {
      return -1;
    }
    return +a < +b ? -1 : 1;
  }
  return a < b ? -1 : 1;
}
export function createRegExp(string: string): RegExp {