Add key based scrolling on magnified screen for kiosk mode.

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index a01990e3f85d5f06dfe9ce57a7837c351c3f897f..0a01a776d4852e3224e8b43befd4b79237fd6bc0 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -119,6 +119,7 @@
 #include "ash/display/display_change_observer_chromeos.h"
 #include "ash/display/display_error_observer_chromeos.h"
 #include "ash/display/output_configurator_animation.h"
+#include "ash/magnifier/magnifier_key_scroller.h"
 #include "base/message_loop/message_pump_x11.h"
 #include "base/sys_info.h"
 #include "chromeos/display/output_configurator.h"
@@ -610,6 +611,10 @@ Shell::~Shell() {
   // Please keep in same order as in Init() because it's easy to miss one.
   if (window_modality_controller_)
     window_modality_controller_.reset();
+#if defined(OS_CHROMEOS) && defined(USE_X11)
+  RemovePreTargetHandler(magnifier_key_scroller_.get());
+  magnifier_key_scroller_.reset();
+#endif
   RemovePreTargetHandler(event_rewriter_filter_.get());
   RemovePreTargetHandler(user_activity_detector_.get());
   RemovePreTargetHandler(overlay_filter_.get());
@@ -810,6 +815,11 @@ void Shell::Init() {
   nested_dispatcher_controller_.reset(new NestedDispatcherController);
   accelerator_controller_.reset(new AcceleratorController);
 
+#if defined(OS_CHROMEOS) && defined(USE_X11)
+  magnifier_key_scroller_.reset(new MagnifierKeyScroller);
+  AddPreTargetHandler(magnifier_key_scroller_.get());
+#endif
+
   // The order in which event filters are added is significant.
   event_rewriter_filter_.reset(new internal::EventRewriterEventFilter);
   AddPreTargetHandler(event_rewriter_filter_.get());