GitLab

Clean up deprecated sources assignment filter in //content/browser

Remove deprecated_default_sources_assignment_filter and replace
it with explicit is_win, is_mac, etc. sections.

Bug: 1018739
Change-Id: I64955cac925925260dd5876ce7a46fda82ba24e0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2445472
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Charlie Reis <creis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814292}