Don't wait for sessions to close on DrmEngine#destroy

[chrisfillmore]

This is a workaround for Chrome bug https://crbug.com/690583.

Resolves #1093

[joeyparrish]

Looks good to me. No reason we have to wait for the session to be closed, if we asked for it to be closed and we are reasonably confident that the browser will close it at some point. It's not an exclusive resource like the video element or MediaSource, so we should be able to move on and still open new sessions later.

[shaka-bot]

All tests passed!

[joeyparrish]

Thanks for the PR! The build bot likes it, I like it, so I'm merging it now.

[joeyparrish]

This is causing failures in offline storage scenarios. I'm going to try to fix it, but I may have to revert your PR.

The problem is that when close() is working correctly, not waiting for it to resolve can cause playback to fail. The Widevine CDM won't let you open the same persistent session twice.

Even when you wait for DrmEngine.destroy() to tell you you're done, the sessions haven't actually been closed yet, so subsequent playback using the same stored session fails (if you're fast enough).

[joeyparrish]

I found a way to fix it. Instead of trusting close() or ignoring it, we can trust it for 1 second, then ignore it if it doesn't resolve in that time. This seems to work in my tests.

[chrisfillmore]

Thanks!

[joeyparrish]

Should be fixed now.