GitLab

The existing iOS recipe utilizes an isolate template, and an
isolated.gen.json file to fill the template in per test with
config-variables and path-variables. This isolate template contains
the command arguments to invoke the iOS test runner.

To support the iOS recipe migration to the Chromium recipe, I use GN to
generate a script per test target instead of the isolate template. The
script is pre-baked with arguments to the test runner (run.py). The
given Swarming task is expected to execute the test by invoking the
generated script.

Invoking the generated script requires changes to gn_isolate_map.pyl
for each iOS test target, and thus, these changes are only additive.

* "ios_test_runner_wrapper" template wraps the generate_wrapper target.
 It bakes iOS specific arguments into the script, such that it can
 launch run.py with the given args.
* ios_eg2_test, ios_eg_test, and test templates have
 been updated to utilize the ios_test_runner_wrapper for iOS targets.
* mb.py to skip generated_directory check when writing isolates.
 View crbug/ in comments.

Change-Id: I941d37dfdff0bd1ead1baff70907a197fee3fe64
Bug: 1055328,912681
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2023748
Commit-Queue: Jeff Yoon <jeffyoon@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#745105}