Add integration test for 'input' event for <input> elements

[frewsxcv]

#9122 merged without any regression tests.

[chkimes]

I'd like to handle this one since I wrote #9122, but I'm unfamiliar with the servo test setup and not sure where to start. Are there some existing tests for events or key press handling that I can use as a reference?

[nox]

@frewsxcv Ew, I'm blind. Sorry for this.

[frewsxcv]

@ckimes89: @nox and I just briefly discussed this on IRC. Considering the input event only gets triggered when the user modifies the value of an <input> element, we might need to wait until we have all the WebDriver commands implemented (#8623). WebDriver is a testing framework similar to Selenium that simulates user interaction

[chkimes]

@frewsxcv @nox It looks like Element Send Keys from WebDriver is already implemented which I think is the only thing needed to test the input event. However, I'm not sure how to use WebDriver in the test suite, are there any examples for this?.

[jdm]

Unfortunately not. That is part of an ongoing project that will hopefully yield useful results to build on.