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

cc/debug/layer_tree_debug_state.h

Index: cc/debug/layer_tree_debug_state.h
diff --git a/cc/debug/layer_tree_debug_state.h b/cc/debug/layer_tree_debug_state.h
index 45cb77c654fcd747440e5fcf0996a8f1ba5c5475..2ea5f9c3aa9f621b43af567ca7bb02d9ef4a285a 100644
--- a/cc/debug/layer_tree_debug_state.h
+++ b/cc/debug/layer_tree_debug_state.h
@@ -5,6 +5,8 @@
 #ifndef CC_DEBUG_LAYER_TREE_DEBUG_STATE_H_
 #define CC_DEBUG_LAYER_TREE_DEBUG_STATE_H_
 
+#include <bitset>
+
 #include "cc/debug/debug_export.h"
 
 namespace cc {
@@ -13,6 +15,14 @@ namespace proto {
 class LayerTreeDebugState;
 }  // namespace proto
 
+enum DebugBorderType {
+  RENDERPASS = 0,
+  SURFACE,
+  LAYER,
+  LAST_DEBUG_BORDER_TYPE = LAYER
+};
+using DebugBorderTypes = std::bitset<LAST_DEBUG_BORDER_TYPE + 1>;
+
 class CC_DEBUG_EXPORT LayerTreeDebugState {
  public:
   LayerTreeDebugState();
@@ -20,7 +30,7 @@ class CC_DEBUG_EXPORT LayerTreeDebugState {
   ~LayerTreeDebugState();
 
   bool show_fps_counter;
-  bool show_debug_borders;
+  DebugBorderTypes show_debug_borders;
 
   bool show_paint_rects;
   bool show_property_changed_rects;