* The testing tsconfig.json inherits from the base TS config.
* A lot of type assertions have been inserted...a lot.
* All testing utilities have migrated to TS.
* text-diff is being replaced with diff for TS compatibility.
* ProtocolError has been added to PuppeteerErrors and PuppeteerErrors is no longer a record (it's been frozen).
* Fixes a small bug where null was an allowable media type in emulation (should be undefined).
Don't ignore stdout and stderr when using pipe for remote debugging and dumpio is true. In that case puppeteer process connects to the stdout/stderr streams of the child process and it will not hang.
