Add persisted preference for projection touch HUD

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index 0ee5b6f16071df3be8ba7d8b0aace1618682d167..ea62e8222f5f53702a593add87dd5b658fcc371b 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -211,8 +211,7 @@ Shell::Shell(ShellDelegate* delegate)
       cursor_manager_(scoped_ptr<views::corewm::NativeCursorManager>(
           native_cursor_manager_)),
       browser_context_(NULL),
-      simulate_modal_window_open_for_testing_(false),
-      is_touch_hud_projection_enabled_(false) {
+      simulate_modal_window_open_for_testing_(false) {
   DCHECK(delegate_.get());
   display_manager_.reset(new internal::DisplayManager);
   mirror_window_controller_.reset(new internal::MirrorWindowController);
@@ -861,10 +860,7 @@ LauncherDelegate* Shell::GetLauncherDelegate() {
   return launcher_delegate_.get();
 }
 
-void Shell::SetTouchHudProjectionEnabled(bool enabled) {
-  if (is_touch_hud_projection_enabled_ == enabled)
-    return;
-
+void Shell::TouchHudProjectionEnabledChanged(bool enabled) {
   RootWindowList roots = GetInstance()->GetAllRootWindows();
   for (RootWindowList::iterator iter = roots.begin(); iter != roots.end();
       ++iter) {
@@ -874,7 +870,6 @@ void Shell::SetTouchHudProjectionEnabled(bool enabled) {
     else
       controller->DisableTouchHudProjection();
   }
-  is_touch_hud_projection_enabled_ = enabled;
 }
 
 void Shell::InitRootWindowForSecondaryDisplay(aura::RootWindow* root) {