ash: Add a heads-up display to track touch-point states and positions.

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index c2fb5a9f04f16c4077e47751b19f906830fb2ed9..ca2e91ea724a8a63bfb4391f08bcbf4062112a47 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -86,6 +86,7 @@ class ShellContextMenu;
 class SystemGestureEventFilter;
 class StackingController;
 class TooltipController;
+class TouchObserverHUD;
 class VisibilityController;
 class WindowModalityController;
 class WorkspaceController;
@@ -368,6 +369,10 @@ class ASH_EXPORT Shell {
   // An event filter that pre-handles all key events to send them to an IME.
   scoped_ptr<aura::shared::InputMethodEventFilter> input_method_filter_;
 
+  // An event filter that silently keeps track of all touch events and controls
+  // a heads-up display. This is enabled only if --ash-touch-hud flag is used.
+  scoped_ptr<internal::TouchObserverHUD> touch_observer_hud_;
+
   // The shelf for managing the launcher and the status widget in non-compact
   // mode. Shell does not own the shelf. Instead, it is owned by container of
   // the status area.