Mac: turn popups into new tabs while in fullscreen.

It's platform convention to show popups as new tabs while in
non-HTML5 fullscreen. (Popups cause tabs to lose HTML5 fullscreen.)

This was implemented for Cocoa in a BrowserWindow override, but
it makes sense to just stick it into Browser and remove a ton
of override code put in just to support this.

BUG=858929, 868416
TEST=as in bugs

Change-Id: I43471f242813ec1159d9c690bab73dab3e610b7d
Reviewed-on: https://chromium-review.googlesource.com/1153455
Reviewed-by: Sidney San Martín <sdy@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#578755}(cherry picked from commit c552cd7b8a0862f6b3c8c6a07f98bda3721101eb)
Reviewed-on: https://chromium-review.googlesource.com/1154508
Reviewed-by: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/branch-heads/3497@{#192}
Cr-Branched-From: 271eaf50594eb818c9295dc78d364aea18c82ea8-refs/heads/master@{#576753}
9 files changed