commit b2d8479c6d85a2d836bdaa340ec450f40c8627f4
author Egor Pasko <pasko@chromium.org> Wed Sep 06 01:43:40 2017
committer Commit Bot <commit-bot@chromium.org> Wed Sep 06 01:43:40 2017
tree 2cb02f8889fc1a9ff52dce3b158bf354f9caad14
parent de4f875fabfb93a869031691869cfcb5ea03455a

Remove a few prerender histograms

This saves ~6.5 KiB of .text on Android by removing expansions of histogram
maros in prerender_histograms.cc. A few macros were converted to their
counterparts from histogram_functions.h, others were removed as no longer
useful.

Cleanup of impossible paths leading to these calls (such as
ORIGIN_OFFLINE or ORIGIN_INSTANT) is postponed for future changes.

Histograms that could still be recorded with nostate-prefetch:

OmniboxPrerenderCount:
  * Can approximate sufficiently from FinalStatus.
TimeSinceLastRecentVisit:
  * Was not used in any of our recent analysis.
PrerendersPerSessionCount:
  * Recorded on iOS, not used in our recent analysis for
    desktop/Android, can approximate with FinalStatus.
TimeBetweenPrerenderRequests
  * Does not look actionable.

Swap-in cannot be triggered any more except with the AMP/CCT flow, where
it swaps over an empty/fake WebContents, which makes the following
histograms no longer interesting:

PercentLoadDoneAtSwapin, OmniboxNavigationsUsedPrerenderCount,
TimeUntilUsed2, AbandonTimeUntilUsed, NetworkBytesUsed.

Bug: 603203, 698733
Change-Id: I193e8748804f7653c676ad2bedd353af739b3b5e
Reviewed-on: https://chromium-review.googlesource.com/647762
Reviewed-by: Matthew Cary <mattcary@chromium.org>
Reviewed-by: Josh Karlin <jkarlin@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Egor Pasko <pasko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#499840}