Fix direction of horizontal scroll when tilting the scroll wheel on Linux Aura

ui/events/x/events_x.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/events/event_constants.h"
 
 #include <cmath>
 #include <string.h>
 #include <X11/extensions/XInput.h>
 #include <X11/extensions/XInput2.h>
@@ skipping 508 matching lines @@
 
   int button = native_event->type == GenericEvent ?
       EventButtonFromNative(native_event) : native_event->xbutton.button;
 
   switch (button) {
     case 4:
       return gfx::Vector2d(0, kWheelScrollAmount);
     case 5:
       return gfx::Vector2d(0, -kWheelScrollAmount);
     case 6:
+      return gfx::Vector2d(kWheelScrollAmount, 0);
+    case 7:
       return gfx::Vector2d(-kWheelScrollAmount, 0);
-    case 7:
-      return gfx::Vector2d(kWheelScrollAmount, 0);
     default:
       return gfx::Vector2d();
   }
 }
 
 void ClearTouchIdIfReleased(const base::NativeEvent& xev) {
   ui::EventType type = ui::EventTypeFromNative(xev);
   if (type == ui::ET_TOUCH_CANCELLED ||
       type == ui::ET_TOUCH_RELEASED) {
     ui::TouchFactory* factory = ui::TouchFactory::GetInstance();
@@ skipping 131 matching lines @@
 
 bool IsNaturalScrollEnabled() {
   return DeviceDataManager::GetInstance()->natural_scroll_enabled();
 }
 
 bool IsTouchpadEvent(const base::NativeEvent& event) {
   return DeviceDataManager::GetInstance()->IsTouchpadXInputEvent(event);
 }
 
 }  // namespace ui