Log to UMA why we would load a third-party frame

Log to UMA why we would load a third-party frame

This will give an estimate of the % of iframes that we can defer
loading.

We can defer offscreen frames unless they are probably used for
cross-origin communication.

Reland of https://codereview.chromium.org/2389023002

BUG=635105
TBR=isherman@chromium.org

Review-Url: https://chromiumcodereview.appspot.com/2437193002
Cr-Commit-Position: refs/heads/master@{#426979}
(cherry picked from commit c301da12f702e16e64faf04524f89bde02ad9588)

Committed: https://chromium.googlesource.com/chromium/src/+/5ca7d242d3f11698547c96b3c2aacd8b5b0171ea

[dgrogan, 2016-10-24 18:38:30]

Description was changed from

==========
Log to UMA why we would load a third-party frame

This will give an estimate of the % of iframes that we can defer
loading.

We can defer offscreen frames unless they are probably used for
cross-origin communication.

Reland of https://codereview.chromium.org/2389023002

BUG=635105
TBR=isherman@chromium.org

Review-Url: https://chromiumcodereview.appspot.com/2437193002
Cr-Commit-Position: refs/heads/master@{#426979}
(cherry picked from commit c301da12f702e16e64faf04524f89bde02ad9588)
==========

to

==========
Log to UMA why we would load a third-party frame

This will give an estimate of the % of iframes that we can defer
loading.

We can defer offscreen frames unless they are probably used for
cross-origin communication.

Reland of https://codereview.chromium.org/2389023002

BUG=635105
TBR=isherman@chromium.org

Review-Url: https://chromiumcodereview.appspot.com/2437193002
Cr-Commit-Position: refs/heads/master@{#426979}
(cherry picked from commit c301da12f702e16e64faf04524f89bde02ad9588)

Committed:
https://chromium.googlesource.com/chromium/src/+/5ca7d242d3f11698547c96b3c2aa...
==========

[dgrogan, 2016-10-24 18:38:31]

Committed patchset #1 (id:1) manually as
5ca7d242d3f11698547c96b3c2aacd8b5b0171ea.