Using leveldb_chrome::PossiblyValidDB in GCMStoreImpl.

Replaced DatabaseExists with new leveldb_chrome::PossiblyValidDB.

Bug: None
Change-Id: Iecb181588355c3f59953230ad0946f8e531c8a3f
Reviewed-on: https://chromium-review.googlesource.com/1090998
Reviewed-by: Dmitry Titov <dimich@chromium.org>
Commit-Queue: Chris Mumford <cmumford@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#567480}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 65d7ba6cb154cf0f4428330fb17232a5064ef0fc
1 file changed