Rename Tab.LockIcon to Tab.SecurityState

The tab's state is concerned with whether or not the page is secure. It should
not mention the lock icon, as this is just a UI choice of how to represent the
security state.

Also renames WebViewController.onUpdatedLockIcon() to onUpdatedSecurityState().

No functional change.

Bug: 5403366
Change-Id: Id18402e84fd9b1f661c160189c7a19a9352fd25c
6 files changed