Don't handle NaturalScroll in Chrome but pass it to CMT instead

chrome/browser/ui/views/ash/tab_scrubber.cc

 // Copyright (c) 2013 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 "chrome/browser/ui/views/ash/tab_scrubber.h"
 
 #include "ash/shell.h"
 #include "ash/wm/window_util.h"
 #include "base/metrics/histogram.h"
 #include "chrome/browser/chrome_notification_types.h"
@@ skipping 91 matching lines @@
 
   if (tab_strip->IsAnimating()) {
     FinishScrub(false);
     return;
   }
 
   // We are handling the event.
   event->StopPropagation();
 
   float x_offset = event->x_offset();
-  if (!ui::IsNaturalScrollEnabled())
-    x_offset = -x_offset;
   int last_tab_index = highlighted_tab_ == -1 ?
       browser->tab_strip_model()->active_index() : highlighted_tab_;
   if (!scrubbing_) {
     swipe_direction_ = (x_offset < 0) ? LEFT : RIGHT;
     const gfx::Point start_point =
         GetStartPoint(tab_strip,
                       browser->tab_strip_model()->active_index(),
                       swipe_direction_);
     browser_ = browser;
     scrubbing_ = true;
@@ skipping 155 matching lines @@
       UMA_HISTOGRAM_CUSTOM_COUNTS("Tabs.ScrubDistance", distance, 0, 20, 20);
       browser_->tab_strip_model()->ActivateTabAt(highlighted_tab_, true);
     }
     tab_strip->RemoveObserver(this);
   }
   swipe_x_ = -1;
   swipe_y_ = -1;
   scrubbing_ = false;
   highlighted_tab_ = -1;
 }