[iOS] Add metrics for actions take on chrome://inspect page.

Log a User Action when the user navigates to the chrome://inspect page and when they take action on the page by Starting and Stopping log collection.

Bug: 899851
Change-Id: Id10d6e113bf5248f853841f7f631568c0b532ea6
Reviewed-on: https://chromium-review.googlesource.com/c/1404740
Commit-Queue: Mike Dougherty <michaeldo@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621769}
4 files changed