Fix installed plugin check

Summary:
D17877108 inadvertently introduced a bug because `fs` and `fs-extra` behave differently and apparently wrapping `exists` which is already async in another `promisify` ends up raising the result as an exception (in this case throwing "true" or "false" as an error instead of yielding it back). Annoyingly, TypeScript's type system doesn't catch this. :/

This fixes the invocation and restores the install/remove functionality.

Reviewed By: jknoxville

Differential Revision: D18199958

fbshipit-source-id: f5835d8912bfe1191a12a318103bfc1fb7d776a3

src/chrome/PluginInstaller.tsx

@@ -26,12 +26,10 @@ import {
   Tooltip,
 } from 'flipper';
 import React, {useCallback, useState, useMemo, useEffect} from 'react';
-import {remote} from 'electron';
 import {List} from 'immutable';
 import algoliasearch from 'algoliasearch';
 import path from 'path';
 import fs from 'fs-extra';
-import {promisify} from 'util';
 import {homedir} from 'os';
 import {PluginManager as PM} from 'live-plugin-manager';
 import {reportPlatformFailures, reportUsage} from '../utils/metrics';
@@ -368,7 +366,7 @@ function useNPMSearch(
 }
 
 async function _getInstalledPlugins(): Promise<Map<string, PluginDefinition>> {
-  const pluginDirExists = await promisify(fs.exists)(PLUGIN_DIR);
+  const pluginDirExists = await fs.pathExists(PLUGIN_DIR);
 
   if (!pluginDirExists) {
     return new Map();