GitLab

In 328d3bee use of leveldb_env::SharedReadCache ceased, but it was
never removed from env_chromium.h.

Bug: None
Change-Id: Idf0e5b16a84b8d3747f70026ffaa55d2cf57dc5b
Reviewed-on: https://chromium-review.googlesource.com/696037Reviewed-by: Daniel Murphy <dmurph@chromium.org>
Commit-Queue: Chris Mumford <cmumford@chromium.org>
Cr-Commit-Position: refs/heads/master@{#505911}