* chore: Use devtools-protocol package
Rather than maintain our own protocol we can instead use the devtools-protocol package and pin it to the version of Chromium that Puppeteer is shipping with.
The only changes are naming changes between the bespoke protocol that Puppeteer created and the devtools-protocol one.
When we merge commits to master, Travis kicks job to build a new commit
and to publish new version of puppeteer@next.
If two commits are landed in almost the same time, then travis starts
two parallel jobs to build each commit. This race condition results
in the incorrect puppeteer@next revision.
This patch teaches apply_next_version.js to verify if current HEAD
is matching upstream HEAD. If it doesn't, the predeploy hook fails
which (hopefully) aborts deployment.
Fixes#2925.
