In order to get more manual test coverage / early feedback for the new experience, we would like to pref on the Pocket Newtab experience in Nightly. It will continue to be pref'd off in Beta/Release until Firefox 68.

Backed out changeset 58286693d6d8 (Bug 1523703) for massive test failures CLOSED TREE

Push with failures: https://treeherder.mozilla.org/#/jobs?repo=autoland&resultStatus=testfailed%2Cbusted%2Cexception&classifiedState=unclassified&revision=58286693d6d8eb1aeab0556ebab1fbf98e83841c&selectedJob=226335256

Failure log: https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=226333914&repo=autoland&lineNumber=1336

Backout: https://hg.mozilla.org/integration/autoland/rev/e8581d168321eb5ecb40c4d4b012bce75485e416

Ohhhh. I see what's python complaining about now.

"{\"enabled\": false}".format()

results in

KeyError: '"enabled"'

because it's expecting something like "{0} {1}".format("hello", "world")

So.. we just need to escape the braces.. with the brace.

"{{\"enabled\": false}}".format()

returns

'{"enabled": false}'

Backed out for bc failures on browser_packaged_as_locales.js

Backout link: https://hg.mozilla.org/integration/autoland/rev/5ebfc44063931b1b0133f86d96558744528c11c9
Push link: https://hg.mozilla.org/integration/autoland/rev/c31a81865825a9d2953e92ea559d38dab138b7df
Log link: https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=226544564&repo=autoland&lineNumber=5753

https://hg.mozilla.org/mozilla-central/rev/a54dbb34bec5

https://hg.mozilla.org/mozilla-central/rev/1b2817234164

https://hg.mozilla.org/mozilla-central/rev/ba5eb152fe23

I have verified this issue with the latest Firefox Beta (67.0b9 Build ID - 20190408123043) and with the latest Firefox Nightly (68.0a1 Build ID - 20190410215612) installed, on Windows 10 x64, Arch Linux and Mac 10.13.3. I can confirm that the new "Pocket Newtab" experience is on by default on Firefox Nightly and pref'd of on Firefox Beta.