Allow scrolling a page with selection after long-press on whitespace

ui/touch_selection/longpress_drag_selector.cc

 // Copyright 2015 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/longpress_drag_selector.h"
 
 #include "base/auto_reset.h"
 #include "ui/events/gesture_detection/motion_event.h"
 
 namespace ui {
@@ skipping 90 matching lines @@
   }
 
   gfx::PointF extent = extend_selection_start ? selection_start : selection_end;
   longpress_drag_selection_offset_ = extent - position;
   client_->OnDragBegin(*this, extent);
   SetState(DRAGGING);
   return true;
 }
 
 bool LongPressDragSelector::IsActive() const {
-  return state_ != INACTIVE && state_ != LONGPRESS_PENDING;
+  return state_ == DRAG_PENDING || state_ == DRAGGING;
 }
 
 void LongPressDragSelector::OnLongPressEvent(base::TimeTicks event_time,
                                              const gfx::PointF& position) {
   // We have no guarantees that the current gesture stream is aligned with the
   // observed touch stream. We only know that the gesture sequence is downstream
   // from the touch sequence. Using a time/distance heuristic helps ensure that
   // the observed longpress corresponds to the active touch sequence.
   if (state_ == LONGPRESS_PENDING &&
       // Ensure the down event occurs *before* the longpress event. Use a
       // small time epsilon to account for floating point time conversion.
       (touch_down_time_ < event_time + base::TimeDelta::FromMicroseconds(10)) &&
       client_->IsWithinTapSlop(touch_down_position_ - position)) {
     SetState(SELECTION_PENDING);
   }
 }
 
+void LongPressDragSelector::OnScrollBeginEvent() {
+  SetState(INACTIVE);
+}
+
 void LongPressDragSelector::OnSelectionActivated() {
   if (state_ == SELECTION_PENDING)
     SetState(DRAG_PENDING);
 }
 
 void LongPressDragSelector::OnSelectionDeactivated() {
   SetState(INACTIVE);
 }
 
 void LongPressDragSelector::SetState(SelectionState state) {
   if (state_ == state)
     return;
 
   const bool was_dragging = state_ == DRAGGING;
   const bool was_active = IsActive();
   state_ = state;
 
   // TODO(jdduke): Add UMA for tracking relative longpress drag frequency.
   if (was_dragging)
     client_->OnDragEnd(*this);
 
   if (was_active != IsActive())
     client_->OnLongPressDragActiveStateChanged();
 }
 
 }  // namespace ui