Merge pull request #14733 from electron/reenable-app-exit-exitCode

test: reenable app module > app.exit(exitCode) > closes all windows

spec/api-app-spec.js

@@ -162,15 +162,7 @@ describe('app module', () => {
       expect(code).to.equal(123)
     })
 
-    // FIXME(alexeykuzmin): Constantly fails with Ch66 on linux,
-    // but looks good with Ch67.
-    // Enable the test after Ch67 is merged into master.
     it('closes all windows', async function () {
-      if (process.platform === 'linux') {
-        this.skip()
-        return
-      }
-
       const appPath = path.join(__dirname, 'fixtures', 'api', 'exit-closes-all-windows-app')
       const electronPath = remote.getGlobal('process').execPath