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Per a suggestion of martinshelton@, this adds a new set of histograms to
track how long users have the Page Info bubble open. This will help us
better understand users who open Page Info but take no actions in it
(e.g., are these opens likely to be more accidental or incidental).

This metric is split by the security level of the page to allow us to
see differences between different security indicators. Two sub-histograms
("Action" and "NoAction") further split up the metric by whether the user
performed an action in the Page Info bubble before closing it (including
actions that cause the bubble to close).

Bug: 859116
Change-Id: I630a1f37ecff13bc7ee44b3e8e5a5c34337c9267
Reviewed-on: https://chromium-review.googlesource.com/1096336
Commit-Queue: Christopher Thompson <cthomp@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Emily Stark <estark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574381}