Output channel doesn't work without timeout

[AndrienkoAleksandr]

Steps to reproduce:

1. Create plugin with such content

import * as theia from '@theia/plugin';

export function start(context: theia.PluginContext) {
    const outputChannel = theia.window.createOutputChannel('Yeoman Generator');
    outputChannel.show(true);
    outputChannel.append("Hello World");
}

export function stop() {

}

2. Run theia with this plugin.
   Expected result: Theia should display Output widget and text "Hello World"
   Actual result: Theia doesn't display output widget at all.
   P.S.: it's somehow begin work when I apply timer, recompile plugin, restart Theia and refresh page few times:

import * as theia from '@theia/plugin';

export function start(context: theia.PluginContext) {
    setTimeout(() => {
        const outputChannel = theia.window.createOutputChannel('Yeoman Generator');
        outputChannel.show(true);
        outputChannel.append("Hello World");
    }, 3000);
}

export function stop() {

}

[AndrienkoAleksandr]

Checked, still actual with 0.3.19. But after #4215 timer workaround is stable: I don't need refresh page few times.

[olexii4]

Cannot reproduce. Tested the last version of Theia(master branch)