NonValidatingReload: Monitor reload operations in NavigationControllerImpl

This patch introduces monitoring reload operations.
This is for reporting metrics on subsequent reload
operations as it is in this patch, and will be used
to manage adaptive reload behaviors later.

BUG=612701
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation

Review-Url: https://codereview.chromium.org/2174293002
Cr-Commit-Position: refs/heads/master@{#421783}
6 files changed