Discovery: impressions metrics are updated each time the new tab page becomes frontmost in a window, even if it was already open. (not when switching back from another window or application). This probably happens not very often in real use but should be fixed.


We can also update multiple times within a single NTP invocation when the user logs in for the first time. First, we record client impressions for TopSites (always at least 2 on desktop--the "welcome" tiles count); then we refresh in-page with MostLikely and get 8 new results.

Maybe this much is working as intended. For this to happen, TopSites must be displayed long enough that a user could decide to navigate to one. However, the MostLikely tiles are also marked as "client"!?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/61b6eba8e654d433215a148f03f7eeac708c73ab

commit 61b6eba8e654d433215a148f03f7eeac708c73ab
Author: sfiera <sfiera@chromium.org>
Date: Fri Jul 15 13:12:28 2016

Record impressions/navigations only once per tile.

Track when we have logged an impression or navigation for a tile, then
ignore it if we are asked to log an additional one for the same tile.
If we detect that the user has returned to the NTP after navigating
away, reset the tracker (and has_emitted_) so that we can collect
stats again.

BUG= 625163 , 626681 

Review-Url: https://codereview.chromium.org/2124903003
Cr-Commit-Position: refs/heads/master@{#405751}

[modify] https://crrev.com/61b6eba8e654d433215a148f03f7eeac708c73ab/chrome/browser/ui/webui/ntp/ntp_user_data_logger.cc
[modify] https://crrev.com/61b6eba8e654d433215a148f03f7eeac708c73ab/chrome/browser/ui/webui/ntp/ntp_user_data_logger.h
[modify] https://crrev.com/61b6eba8e654d433215a148f03f7eeac708c73ab/chrome/browser/ui/webui/ntp/ntp_user_data_logger_unittest.cc