Add traffic annotation to download Plugin VM image request

Defines plugin_vm_image_download traffic annotation and adds it to the
corresponding request.

Bug: 966399
Change-Id: Iefbc4a6f11385aaf80f99971c7365872297a0c1f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1648162
Reviewed-by: Christian Dullweber <dullweber@chromium.org>
Reviewed-by: Alex Oldemeier <aoldemeier@chromium.org>
Commit-Queue: Olya Kalitova <okalitova@chromium.org>
Cr-Commit-Position: refs/heads/master@{#668027}
1 file changed