Extensions: Remove unused Warning::CreateNetworkConflictWarning.

This CL removes the unused method Warning::CreateNetworkConflictWarning. It
seems to have been introduced in r167673 without any usages.

BUG=111700

Change-Id: I4f209bbcabafd0f19203f970dab8341c97a256eb
Reviewed-on: https://chromium-review.googlesource.com/1148170
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Karan Bhatia <karandeepb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577669}
5 files changed