Release mouse pointer capture when it starts drag

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 546 matching lines @@
            .IsNone() &&
       !capturing_mouse_events_node_) {
     return i_beam;
   }
 
   if (ShouldShowIBeamForNode(node, result))
     return i_beam;
   return PointerCursor();
 }
 
+WebInputEventResult EventHandler::HandlePointerEvent(
+    const WebPointerEvent& web_pointer_event,
+    Node* target) {
+  return pointer_event_manager_->HandlePointerEvent(web_pointer_event, target);
+}
+
 WebInputEventResult EventHandler::HandleMousePressEvent(
     const WebMouseEvent& mouse_event) {
   TRACE_EVENT0("blink", "EventHandler::handleMousePressEvent");
 
   // For 4th/5th button in the mouse since Chrome does not yet send
   // button value to Blink but in some cases it does send the event.
   // This check is needed to suppress such an event (crbug.com/574959)
   if (mouse_event.button == WebPointerProperties::Button::kNoButton)
     return WebInputEventResult::kHandledSuppressed;
 
@@ skipping 1519 matching lines @@
     MouseEventWithHitTestResults& mev,
     LocalFrame* subframe) {
   WebInputEventResult result =
       subframe->GetEventHandler().HandleMouseReleaseEvent(mev.Event());
   if (result != WebInputEventResult::kNotHandled)
     return result;
   return WebInputEventResult::kHandledSystem;
 }
 
 }  // namespace blink