Remove --ash-enable-tray-dragging flag

ash/wm/gestures/shelf_gesture_handler.cc

Index: ash/wm/gestures/shelf_gesture_handler.cc
diff --git a/ash/wm/gestures/shelf_gesture_handler.cc b/ash/wm/gestures/shelf_gesture_handler.cc
index 6d4a01aab56b1699005c4ff4d3e7e4ad3c6e6a75..eb485ad2d1890a342dac6a636da531272797b04b 100644
--- a/ash/wm/gestures/shelf_gesture_handler.cc
+++ b/ash/wm/gestures/shelf_gesture_handler.cc
@@ -11,7 +11,6 @@
 #include "ash/shelf/shelf_widget.h"
 #include "ash/shell.h"
 #include "ash/system/status_area_widget.h"
-#include "ash/wm/gestures/tray_gesture_handler.h"
 #include "ash/wm/window_state.h"
 #include "ash/wm/window_util.h"
 #include "ui/aura/window.h"
@@ -63,14 +62,7 @@ bool ShelfGestureHandler::ProcessGestureEvent(const ui::GestureEvent& event) {
     return false;
 
   if (event.type() == ui::ET_GESTURE_SCROLL_UPDATE) {
-    if (tray_handler_) {
-      if (!tray_handler_->UpdateGestureDrag(event))
-        tray_handler_.reset();
-    } else if (shelf->UpdateGestureDrag(event) ==
-        ShelfLayoutManager::DRAG_TRAY) {
-      tray_handler_.reset(new TrayGestureHandler());
-    }
-
+    shelf->UpdateGestureDrag(event);
     return true;
   }
 
@@ -78,11 +70,6 @@ bool ShelfGestureHandler::ProcessGestureEvent(const ui::GestureEvent& event) {
 
   if (event.type() == ui::ET_GESTURE_SCROLL_END ||
       event.type() == ui::ET_SCROLL_FLING_START) {
-    if (tray_handler_) {
-      tray_handler_->CompleteGestureDrag(event);
-      tray_handler_.reset();
-    }
-
     shelf->CompleteGestureDrag(event);
     return true;
   }