This patch:
- adds `page.touchscreen` namespace, similar to `page.mouse` and `page.keyboard`.
- adds tapping to multiple layers:
- `page.touchscreen.tap`
- `page.tap` - convenience method which accepts selector
- `elementHandle.tap`
Fixes#568 and #569.
This patch:
- removes the `page.uploadFile` method
- adds `elementHandle.uploadFile` method.
Motivation: `elementHandle.uploadFile` is rarely used, so it doesn't worth it
to keep it on page.
This patch:
- rolls chromium to r494365
- starts using Runtime.evaluate(awaitPromise: true), with new semantic
we can avoid additional Runtime.awaitPromise call
- stops resolving promises for Console event
