Code:  void TabGroupHeader::OnPaint(gfx::Canvas* canvas) {
  constexpr SkColor kPlaceholderColor = SkColorSetRGB(0xAA, 0xBB, 0xCC);
   gfx::Rect fill_bounds(GetLocalBounds());
   fill_bounds.Inset(TabStyle::GetTabOverlap(), 0);
  canvas->FillRect(fill_bounds, kPlaceholderColor);
 }

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}