Selection API: Add a UseCounter for focus change by Selection.modify().

third_party/WebKit/Source/core/editing/DOMSelection.cpp

 /*
  * Copyright (C) 2007, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * 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
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 418 matching lines @@
     granularity = LineBoundary;
   else if (equalIgnoringCase(granularityString, "sentenceboundary"))
     granularity = SentenceBoundary;
   else if (equalIgnoringCase(granularityString, "paragraphboundary"))
     granularity = ParagraphBoundary;
   else if (equalIgnoringCase(granularityString, "documentboundary"))
     granularity = DocumentBoundary;
   else
     return;
 
+  Element* focusedElement = frame()->document()->focusedElement();
   frame()->selection().modify(alter, direction, granularity);
+  if (frame() && frame()->document() &&
+      focusedElement != frame()->document()->focusedElement())
+    UseCounter::count(frame(), UseCounter::SelectionFuncionsChangeFocus);
 }
 
 // https://www.w3.org/TR/selection-api/#dom-selection-extend
 void DOMSelection::extend(Node* node,
                           unsigned offset,
                           ExceptionState& exceptionState) {
   DCHECK(node);
   if (!isAvailable())
     return;
 
@@ skipping 360 matching lines @@
     m_treeScope->document().addConsoleMessage(
         ConsoleMessage::create(JSMessageSource, ErrorMessageLevel, message));
 }
 
 DEFINE_TRACE(DOMSelection) {
   visitor->trace(m_treeScope);
   ContextClient::trace(visitor);
 }
 
 }  // namespace blink