views: add focus ring to TreeView

ui/views/controls/focus_ring.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/controls/focus_ring.h"
 
 #include "ui/gfx/canvas.h"
 #include "ui/native_theme/native_theme.h"
 #include "ui/views/controls/focusable_border.h"
 
@@ skipping 16 matching lines @@
       return static_cast<FocusRing*>(parent->child_at(i));
   }
   return nullptr;
 }
 
 }  // namespace
 
 const char FocusRing::kViewClassName[] = "FocusRing";
 
 // static
-void FocusRing::Install(views::View* parent,
-                        ui::NativeTheme::ColorId override_color_id) {
+views::View* FocusRing::Install(views::View* parent,
+                                ui::NativeTheme::ColorId override_color_id) {
   DCHECK(parent->HasFocus());
   FocusRing* ring = GetFocusRing(parent);
   if (!ring) {
     ring = new FocusRing();
     parent->AddChildView(ring);
   }
   ring->override_color_id_ = override_color_id;
   ring->Layout();
   ring->SchedulePaint();
+  return ring;
 }
 
 // static
 void FocusRing::Uninstall(views::View* parent) {
   delete GetFocusRing(parent);
 }
 
 const char* FocusRing::GetClassName() const {
   return kViewClassName;
 }
@@ skipping 29 matching lines @@
 FocusRing::FocusRing()
     : override_color_id_(ui::NativeTheme::kColorId_NumColors) {
   // A layer is necessary to paint beyond the parent's bounds.
   SetPaintToLayer(true);
   layer()->SetFillsBoundsOpaquely(false);
 }
 
 FocusRing::~FocusRing() {}
 
 }  // namespace views