Emit change event on uploadFile calls

[phihag]

In puppeteer 1.20.0, the following code emitted an alert:

const puppeteer = require('puppeteer');

(async () => {
	const browser = await puppeteer.launch({args: ['--no-sandbox'], headless: false});
	const page = (await browser.pages())[0];

	await page.setContent(`
		<input type=file>
		<script>
		document.querySelector('input').addEventListener('change', () => {
			alert('Uploaded a file');
		});
		</script>
		`);
	const input = await page.waitForSelector('input[type="file"]');
	await input.uploadFile(__filename);
})();

This is broken in puppeteer 2.0.0 and 2.1.0.
A bisection yielded 6091a34 as the commit that broke this.

Emitting the change event as well seems to fix the problem.

[mathiasbynens]

Thanks for the patch! Could you add a test for this as well please?

[heikkipora]

This PR (and bug) is related to the same file upload changeset: #5358 (and should be merged at the same time with this PR I think)

[phihag]

Updated to include tests for the input and change events.

[SimonSchick]

Test failures seem unrelated to code changes.