First crack at implementing the touch explaration mode.

ash/root_window_controller.cc

Index: ash/root_window_controller.cc
diff --git a/ash/root_window_controller.cc b/ash/root_window_controller.cc
index caa1228890e223325fdbf44c9f3b658fbb2d0b0d..8774ec637555562bb54ec82211171aa61e2054ba 100644
--- a/ash/root_window_controller.cc
+++ b/ash/root_window_controller.cc
@@ -27,6 +27,7 @@
 #include "ash/switchable_windows.h"
 #include "ash/system/status_area_widget.h"
 #include "ash/system/tray/system_tray_delegate.h"
+#include "ash/system/tray/system_tray_notifier.h"
 #include "ash/touch/touch_hud_debug.h"
 #include "ash/touch/touch_hud_projection.h"
 #include "ash/touch/touch_observer_hud.h"
@@ -713,6 +714,9 @@ void RootWindowController::Init(RootWindowType root_window_type,
     if (shell->session_state_delegate()->NumberOfLoggedInUsers())
       shelf()->CreateShelf();
   }
+
+  Shell::GetInstance()->system_tray_notifier()->AddAccessibilityObserver(this);
+  UpdateTouchExplorationState();
 }
 
 void RootWindowController::InitLayoutManagers() {
@@ -1009,6 +1013,26 @@ void RootWindowController::OnTouchHudProjectionToggled(bool enabled) {
     DisableTouchHudProjection();
 }
 
+void RootWindowController::UpdateTouchExplorationState() {
+  AccessibilityDelegate* delegate =
+        Shell::GetInstance()->accessibility_delegate();
+  bool enabled = delegate->IsSpokenFeedbackEnabled();
+
+  LOG(ERROR) << "RWC::UpdateTouchExplorationState: enabled=" << enabled;
+
+  if (enabled && !touch_exploration_controller_.get()) {
+    touch_exploration_controller_.reset(
+        new TouchExplorationController(root_window()));
+  } else if (!enabled && touch_exploration_controller_.get()) {
+    touch_exploration_controller_.reset();
+  }
+}
+
+void RootWindowController::OnAccessibilityModeChanged(
+      AccessibilityNotificationVisibility notify) {
+  UpdateTouchExplorationState();
+}
+
 RootWindowController* GetRootWindowController(
     const aura::Window* root_window) {
   return root_window ? GetRootWindowSettings(root_window)->controller : NULL;