Embed pdf compositor service in Headless Chrome

Add the support to use packaged services in Headless Chrome. Also pack
pdf compositor service into it. Enable launching the service as an out of
process utility process.

BUG=455764

Change-Id: I385f18b918ef541b0937dd2f41679fa4a43f2d62
Reviewed-on: https://chromium-review.googlesource.com/614385
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Eric Seckler <eseckler@chromium.org>
Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
Commit-Queue: Wei Li <weili@chromium.org>
Cr-Commit-Position: refs/heads/master@{#497930}
15 files changed