Implement a Hit Test Cache.

Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 1209 matching lines @@
     if (!layoutView())
         return Vector<Element*>();
     return TreeScope::elementsFromPoint(x, y);
 }
 
 PassRefPtrWillBeRawPtr<Range> Document::caretRangeFromPoint(int x, int y)
 {
     if (!layoutView())
         return nullptr;
 
-    HitTestResult result = hitTestInDocument(this, x, y);
+    HitTestResult result = hitTestInDocument(this, x, y, true);

[Rick Byers, 2015/06/05 20:48:59]

This pattern is generally frowned upon in Google C++, see the true/false part of
http://google.github.io/styleguide/cppguide.html#Implementation_Comments

If skipping the cache is unusual, then I'd suggest having a
hitTestInDocumentNoCache method and leaving the 3 arg method alone.  Alternately
you could use an enum instead of a bool or (usually lowest preference) add a
comment at each call site saying what the true/false means.

[esprehn, 2015/06/06 21:14:29]

Yes, please no bools like this.

[dtapuska, 2015/06/09 18:21:23]

Done.

[dtapuska, 2015/06/09 18:21:23]

Done.

     PositionWithAffinity positionWithAffinity = result.position();
     if (positionWithAffinity.position().isNull())
         return nullptr;
 
     Position rangeCompliantPosition = positionWithAffinity.position().parentAnchoredEquivalent();
     return Range::createAdjustedToTreeScope(*this, rangeCompliantPosition);
 }
 
 Element* Document::scrollingElement()
 {
@@ skipping 4447 matching lines @@
 #ifndef NDEBUG
 using namespace blink;
 void showLiveDocumentInstances()
 {
     WeakDocumentSet& set = liveDocumentSet();
     fprintf(stderr, "There are %u documents currently alive:\n", set.size());
     for (Document* document : set)
         fprintf(stderr, "- Document %p URL: %s\n", document, document->url().string().utf8().data());
 }
 #endif