ui: Add debug flag to show composited layer borders in ChromeOS UI.

content/renderer/gpu/render_widget_compositor.cc

Index: content/renderer/gpu/render_widget_compositor.cc
diff --git a/content/renderer/gpu/render_widget_compositor.cc b/content/renderer/gpu/render_widget_compositor.cc
index 3d535c5afcbdfab438c0c03d3ac2f09c8f4a4497..ed8514c2c22fea17601d18953ab7295e2f219f18 100644
--- a/content/renderer/gpu/render_widget_compositor.cc
+++ b/content/renderer/gpu/render_widget_compositor.cc
@@ -354,8 +354,8 @@ cc::LayerTreeSettings RenderWidgetCompositor::GenerateLayerTreeSettings(
   settings.single_thread_proxy_scheduler = false;
 
   // These flags should be mirrored by UI versions in ui/compositor/.
-  settings.initial_debug_state.show_debug_borders =
-      cmd.HasSwitch(cc::switches::kShowCompositedLayerBorders);
+  if (cmd.HasSwitch(cc::switches::kShowCompositedLayerBorders))
+    settings.initial_debug_state.show_debug_borders.set();
   settings.initial_debug_state.show_layer_animation_bounds_rects =
       cmd.HasSwitch(cc::switches::kShowLayerAnimationBounds);
   settings.initial_debug_state.show_paint_rects =