GitLab

Kill the lowest ranked connection when there are no more service slots
when trying to allocate a new connection.

Remove the hack solution that passed down the number of service slots
to RenderProcessHost::GetMaxRendererProcessCount.
Remove releaseAllModerateBindings when the last service is allocated.
Add a test in content that verifies intentional kill works.

Refactored ChildConnectionAllocator to make the queuing of requests
explicit. Then add a callback when Allocator runs out of slots for
allocation which content layer handles by killing the lowest ranked
connection. This implementation ensures there is only one connection
being killed waiting to be noticed.

Change-Id: I5f670dfcf6ce645ab2681ec97d095eca98b2b5a2
Reviewed-on: https://chromium-review.googlesource.com/1002193
Commit-Queue: Bo <boliu@chromium.org>
Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Reviewed-by: Maria Khomenko <mariakhomenko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556329}