Clear the state of scroll and selection onmouseup

third_party/WebKit/Source/core/input/EventHandler.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights
  * reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2012 Digia Plc. and/or its subsidiary(-ies)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
@@ skipping 985 matching lines @@
       EventTypeNames::mouseup, mev.InnerNode(), mev.CanvasRegionId(),
       mev.Event(), Vector<WebMouseEvent>());
 
   WebInputEventResult click_event_result =
       mouse_release_target ? mouse_event_manager_->DispatchMouseClickIfNeeded(
                                  mev, *mouse_release_target)
                            : WebInputEventResult::kNotHandled;
 
   scroll_manager_->ClearResizeScrollableArea(false);
 
-  if (event_result == WebInputEventResult::kNotHandled)
-    event_result = mouse_event_manager_->HandleMouseReleaseEvent(mev);
+  WebInputEventResult selection_scroll_event_result =
+      mouse_event_manager_->HandleMouseReleaseEvent(mev);

[dtapuska, 2017/05/08 18:54:07]

What about preventing the paste on middle click result..

https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/editing/S...

?

   mouse_event_manager_->ClearDragHeuristicState();
 
   mouse_event_manager_->InvalidateClick();
 
-  return EventHandlingUtil::MergeEventResult(click_event_result, event_result);
+  return EventHandlingUtil::MergeEventResult(
+      EventHandlingUtil::MergeEventResult(click_event_result, event_result),
+      selection_scroll_event_result);
 }
 
 static bool TargetIsFrame(Node* target, LocalFrame*& frame) {
   if (!IsHTMLFrameElementBase(target))
     return false;
 
   // Cross-process drag and drop is not yet supported.
   if (ToHTMLFrameElementBase(target)->ContentFrame() &&
       !ToHTMLFrameElementBase(target)->ContentFrame()->IsLocalFrame())
     return false;
@@ skipping 1094 matching lines @@
     MouseEventWithHitTestResults& mev,
     LocalFrame* subframe) {
   WebInputEventResult result =
       subframe->GetEventHandler().HandleMouseReleaseEvent(mev.Event());
   if (result != WebInputEventResult::kNotHandled)
     return result;
   return WebInputEventResult::kHandledSystem;
 }
 
 }  // namespace blink