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

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index c0a555f40681e5d46a5b04c2d86df0c626e18f93..663d7e1807a9a18e18daa7aea128e41f68196c8d 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -27,6 +27,7 @@
 #include "ash/system/tray/system_tray.h"
 #include "ash/system/tray/system_tray_delegate.h"
 #include "ash/tooltips/tooltip_controller.h"
+#include "ash/touch/touch_observer_hud.h"
 #include "ash/wm/activation_controller.h"
 #include "ash/wm/app_list_controller.h"
 #include "ash/wm/base_layout_manager.h"
@@ -553,6 +554,8 @@ Shell::~Shell() {
 #if !defined(OS_MACOSX)
   RemoveRootWindowEventFilter(accelerator_filter_.get());
 #endif
+  if (touch_observer_hud_.get())
+    RemoveRootWindowEventFilter(touch_observer_hud_.get());
 
   // Close background widget now so that the focus manager of the
   // widget gets deleted in the final message loop run.
@@ -684,6 +687,13 @@ void Shell::Init() {
 
   CreateSpecialContainers(root_window);
 
+  CommandLine* command_line = CommandLine::ForCurrentProcess();
+
+  if (command_line->HasSwitch(switches::kAshTouchHud)) {
+    touch_observer_hud_.reset(new internal::TouchObserverHUD);
+    AddRootWindowEventFilter(touch_observer_hud_.get());
+  }
+
   stacking_controller_.reset(new internal::StackingController);
 
   root_window_layout_ = new internal::RootWindowLayoutManager(root_window);
@@ -691,8 +701,6 @@ void Shell::Init() {
 
   event_client_.reset(new internal::EventClientImpl(root_window));
 
-  CommandLine* command_line = CommandLine::ForCurrentProcess();
-
   tray_.reset(new SystemTray());
   if (delegate_.get())
     tray_delegate_.reset(delegate_->CreateSystemTrayDelegate(tray_.get()));