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 a42e46b22199e628aae565ac28d5dcab7510077d..e39d265f15c7d32dd1a3c0ba9a69540ac2a0d93f 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -120,6 +120,7 @@
 #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"
@@ -617,6 +618,10 @@ 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());
@@ -817,6 +822,11 @@ 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());