ui: Enable debug borders for the UI compositor through layer tree settings.

ui/compositor/compositor.cc

 // Copyright (c) 2012 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/compositor/compositor.h"
 
 #include <algorithm>
 #include <deque>
 
 #include "base/bind.h"
@@ skipping 287 matching lines @@
       WebKit::Platform::current()->compositorSupport();
   root_web_layer_.reset(compositor_support->createLayer());
   WebKit::WebLayerTreeView::Settings settings;
   CommandLine* command_line = CommandLine::ForCurrentProcess();
   settings.showFPSCounter =
       command_line->HasSwitch(switches::kUIShowFPSCounter);
   settings.showPlatformLayerTree =
       command_line->HasSwitch(switches::kUIShowLayerTree);
   settings.refreshRate =
       test_compositor_enabled ? kTestRefreshRate : kDefaultRefreshRate;
+  settings.showDebugBorders =
+      command_line->HasSwitch(switches::kUIShowLayerBorders);
 
   root_web_layer_->setAnchorPoint(WebKit::WebFloatPoint(0.f, 0.f));
   host_.reset(compositor_support->createLayerTreeView(this, *root_web_layer_,
                                                       settings));
   host_->setSurfaceReady();
 }
 
 Compositor::~Compositor() {
   CancelCompositorLock();
   DCHECK(!compositor_lock_);
@@ skipping 258 matching lines @@
 
 COMPOSITOR_EXPORT void DisableTestCompositor() {
   test_compositor_enabled = false;
 }
 
 COMPOSITOR_EXPORT bool IsTestCompositorEnabled() {
   return test_compositor_enabled;
 }
 
 }  // namespace ui