Avoid creating null throttle entry in map.

A recent change (master@{#577718}) landed a temp fix for a null
pointer dereference to avoid a crash. This change first looks
for the entry in the entry map to avoid creating a new map
value with a null entry pointer.

Bug: 866798,867430
Change-Id: Ie8ab1ada4ff34faa22db738c1862a71fe3c297e3
Reviewed-on: https://chromium-review.googlesource.com/1150215
Reviewed-by: Nick Harper <nharper@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Chris Mumford <cmumford@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578055}
3 files changed