mash: Remove ash::ShelfGestureHandler and ui::ET_GESTURE_WIN8_EDGE_SWIPE

ash/aura/wm_shelf_aura.cc

Index: ash/aura/wm_shelf_aura.cc
diff --git a/ash/aura/wm_shelf_aura.cc b/ash/aura/wm_shelf_aura.cc
index 5d70a393b9f88343a9cc47b74bf7a9cd094c764f..84c7892d57112798116ca0b4ba6864a4c6a79877 100644
--- a/ash/aura/wm_shelf_aura.cc
+++ b/ash/aura/wm_shelf_aura.cc
@@ -133,10 +133,11 @@ gfx::Rect WmShelfAura::GetScreenBoundsOfItemIconForWindow(WmWindow* window) {
       WmWindowAura::GetAuraWindow(window));
 }
 
-bool WmShelfAura::ProcessGestureEvent(const ui::GestureEvent& event,
-                                      WmWindow* target_window) {
-  return gesture_handler_.ProcessGestureEvent(
-      event, WmWindowAura::GetAuraWindow(target_window));
+bool WmShelfAura::ProcessGestureEvent(const ui::GestureEvent& event) {
+  // Can be called at login screen.
+  if (!shelf_layout_manager_)
+    return false;
+  return shelf_layout_manager_->ProcessGestureEvent(event);
 }
 
 void WmShelfAura::UpdateAutoHideForMouseEvent(ui::MouseEvent* event) {