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-Commit-Position: refs/heads/master@{#578755}
void BrowserView::PaintChildren(const views::PaintInfo& paint_info) {
  views::ClientView::PaintChildren(paint_info);
  if (!histogram_helper_) {
    histogram_helper_ = BrowserWindowHistogramHelper::
        MaybeRecordValueAndCreateInstanceOnBrowserPaint(
            GetWidget()->GetCompositor());
  }
}

void BrowserView::PaintChildren(const views::PaintInfo& paint_info) {
  views::ClientView::PaintChildren(paint_info);
  if (!histogram_helper_) {
    histogram_helper_ = BrowserWindowHistogramHelper::
        MaybeRecordValueAndCreateInstanceOnBrowserPaint(
            GetWidget()->GetCompositor());
  }
}
