Without this, gn-built isolates do not include the test expectations
file in the isolate, causing the test suite to bail out at startup.
Also rename target_name to api_name as target_name is a special
variable name when inside a target definition.

BUG=580045

Change-Id: I20be39c7e50e24757a0828f9056613e171f0002f
Reviewed-on: https://chromium-review.googlesource.com/325040Tested-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>