Code:  void TabStrip::ChangeTabGroup(int model_index,
                               base::Optional<int> old_group,
                               base::Optional<int> new_group) {
   if (new_group.has_value() && !group_headers_[new_group.value()]) {
    const TabGroupData* group_data =
        controller_->GetDataForGroup(new_group.value());
    auto header = std::make_unique<TabGroupHeader>(group_data->title());
     header->set_owned_by_client();
     AddChildView(header.get());
     group_headers_[new_group.value()] = std::move(header);
  }
  if (old_group.has_value() &&
      controller_->ListTabsInGroup(old_group.value()).size() == 0) {
    group_headers_.erase(old_group.value());
  }
  UpdateIdealBounds();
  AnimateToIdealBounds();
}

Vulnerability Type: 
CWE ID: CWE-20
Summary: The extensions API in Google Chrome prior to 55.0.2883.75 for Mac, Windows and Linux, and 55.0.2883.84 for Android incorrectly handled navigation within PDFs, which allowed a remote attacker to temporarily spoof the contents of the Omnibox (URL bar) via a crafted HTML page containing PDF data.
Commit Message: 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}