Swap touch selection handles when they are interchanged

ui/touch_selection/touch_selection_controller.cc

 // Copyright 2014 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/touch_selection/touch_selection_controller.h"
 
 #include "base/auto_reset.h"
 #include "base/logging.h"
 #include "base/metrics/histogram_macros.h"
 
@@ skipping 71 matching lines @@
 
   // Notify if selection bounds have just been established or dissolved.
   if (start.type() != SelectionBound::EMPTY &&
       start_.type() == SelectionBound::EMPTY) {
     client_->OnSelectionEvent(SELECTION_ESTABLISHED);
   } else if (start.type() == SelectionBound::EMPTY &&
              start_.type() != SelectionBound::EMPTY) {
     client_->OnSelectionEvent(SELECTION_DISSOLVED);
   }
 
+  // Swap the Handles when the start and end selection points cross each other.
+  if (active_status_ == SELECTION_ACTIVE) {
+    if ((start_selection_handle_->IsActive() &&
+         end_.edge_bottom() == start.edge_bottom()) ||
+        (end_selection_handle_->IsActive() &&
+         end.edge_bottom() == start_.edge_bottom())) {
+      start_selection_handle_.swap(end_selection_handle_);
+    }
+  }
+
   start_ = start;
   end_ = end;
   start_orientation_ = ToTouchHandleOrientation(start_.type());
   end_orientation_ = ToTouchHandleOrientation(end_.type());
   force_next_update_ = false;
 
   if (!activate_selection_automatically_ &&
       !activate_insertion_automatically_) {
     DCHECK_EQ(INACTIVE, active_status_);
     DCHECK_EQ(INPUT_EVENT_TYPE_NONE, response_pending_input_event_);
@@ skipping 559 matching lines @@
     base::TimeDelta duration = base::TimeTicks::Now() - selection_start_time_;
     UMA_HISTOGRAM_CUSTOM_TIMES("Event.TouchSelection.WasDraggedDuration",
                                duration,
                                base::TimeDelta::FromMilliseconds(500),
                                base::TimeDelta::FromSeconds(60),
                                60);
   }
 }
 
 }  // namespace ui