[Telemetry] Expose browser startup args
[Telemetry] Expose browser startup args

Stores and exposes the startup args used to create a Browser object.
Some users of Telemetry such as the GPU tests need to know what
arguments a browser was started with. Currently, they do this by
checking a browser's _browser_backend.browser_options.extra_browser_args
list, but simply exposing the startup args is more complete and prevents
the need to access protected members.

Bug: chromium:1076144
Change-Id: I0028187bf1fce2ef2fcc2faea4d33f17b7695abe
Reviewed-on: https://chromium-review.googlesource.com/c/catapult/+/2175112
Commit-Queue: Brian Sheedy <8cdc5cc1fa60ba15acb0d296e6f5592b7bb7d71c@chromium.org>
Commit-Queue: John Chen <334fbfbb4df7c78f091ea1b77c69ca6ac731a3f3@chromium.org>
Auto-Submit: Brian Sheedy <8cdc5cc1fa60ba15acb0d296e6f5592b7bb7d71c@chromium.org>
Reviewed-by: John Chen <334fbfbb4df7c78f091ea1b77c69ca6ac731a3f3@chromium.org>

catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult