GitLab

1. Add an extra error param to GetEngineIfActive, so that we can tell if
it fails because the engine is unavailable or inactive.
2. Add LOGs for engine errors.
3. Add error handling to more functions.
4. Add some helper functions to reduce code duplication.
5. Minor change on constants name for readability.
6. Disable some browser tests, they were actually testing nothing before (because there was no active engine, they actually skipped everything...). Eventually we should rewrite those tests in the new fashion as https://cs.chromium.org/chromium/src/chrome/browser/chromeos/input_method/input_method_engine_browsertests.cc

R=keithlee, shend, shuchen

Bug: 1024606
Change-Id: I9902e42a472122c5c1a02c36e70f71b52cdd80d1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1933855Reviewed-by: Keith Lee <keithlee@chromium.org>
Reviewed-by: Shu Chen <shuchen@chromium.org>
Reviewed-by: Darren Shen <shend@chromium.org>
Commit-Queue: Keith Lee <keithlee@chromium.org>
Commit-Queue: Jing Wang <jiwan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719454}