Roll engine 49dbaae818cd..3a445edda924 (4 commits) (#42251)

git@github.com:flutter/engine.git/compare/49dbaae818cd...3a445edda924

git log 49dbaae818cd..3a445edda924 --no-merges --oneline
2019-10-08 30870216+gaaclarke@users.noreply.github.com Made _printDebug only happen on debug builds of the engine for now. (flutter/engine#12980)
2019-10-08 devoncarew@google.com remove references to package:_chrome (flutter/engine#12931)
2019-10-08 ditman@gmail.com Open source canvas tests from flutter_web_ui (flutter/engine#12819)
2019-10-08 mouad.debbar@gmail.com Prevent default when Tab is clicked (flutter/engine#12986)


If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-engine-flutter-autoroll
Please CC chinmaygarde@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md