Paint tab groups with the group color.

* The background of TabGroupHeader now uses the group color.
* The backgrounds of tabs in the group are tinted with the group color.

This treatment, along with the colors chosen, are intended to be
a placeholder.

Bug: 905491
Change-Id: Ic808548f8eba23064606e7fb8c9bba281d0d117f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1610504
Commit-Queue: Bret Sepulveda <bsep@chromium.org>
Reviewed-by: Taylor Bergquist <tbergquist@chromium.org>
Cr-Commit-Position: refs/heads/master@{#660498}
bool TabStrip::IsPointInTab(Tab* tab,
                            const gfx::Point& point_in_tabstrip_coords) {
  if (!tab->GetVisible())
    return false;
  gfx::Point point_in_tab_coords(point_in_tabstrip_coords);
  View::ConvertPointToTarget(this, tab, &point_in_tab_coords);
  return tab->HitTestPoint(point_in_tab_coords);
}

bool TabStrip::IsPointInTab(Tab* tab,
                            const gfx::Point& point_in_tabstrip_coords) {
  if (!tab->GetVisible())
    return false;
  gfx::Point point_in_tab_coords(point_in_tabstrip_coords);
  View::ConvertPointToTarget(this, tab, &point_in_tab_coords);
  return tab->HitTestPoint(point_in_tab_coords);
}
