[WIP] Allow scroll events to permanently change the default gesture handler in RootView

ui/views/controls/scrollbar/base_scroll_bar.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/views/controls/scrollbar/base_scroll_bar.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "base/compiler_specific.h"
@@ skipping 182 matching lines @@
   return false;
 }
 
 bool BaseScrollBar::OnMouseWheel(const ui::MouseWheelEvent& event) {
   ScrollByContentsOffset(event.y_offset());
   return true;
 }
 
 void BaseScrollBar::OnGestureEvent(ui::GestureEvent* event) {
   // If a fling is in progress, then stop the fling for any incoming gesture
-  // event (except for the GESTURE_END event that is generated at the end of the
-  // fling).
-  if (scroll_animator_.get() && scroll_animator_->is_scrolling() &&
-      (event->type() != ui::ET_GESTURE_END ||
-       event->details().touch_points() > 1)) {
+  // event.
+  if (scroll_animator_.get() && scroll_animator_->is_scrolling())
     scroll_animator_->Stop();
-  }
 
   if (event->type() == ui::ET_GESTURE_TAP_DOWN) {
     ProcessPressEvent(*event);
     event->SetHandled();
     return;
   }
 
   if (event->type() == ui::ET_GESTURE_LONG_PRESS) {
     // For a long-press, the repeater started in tap-down should continue. So
     // return early.
@@ skipping 288 matching lines @@
     thumb_position = thumb_position - (thumb_->GetSize() / 2);
   return (thumb_position * contents_size_) / GetTrackSize();
 }
 
 void BaseScrollBar::SetThumbTrackState(CustomButton::ButtonState state) {
   thumb_track_state_ = state;
   SchedulePaint();
 }
 
 }  // namespace views