Add a fast-path for independent inherited properties

third_party/WebKit/Source/core/dom/Element.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003-2011, 2013, 2014 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 631 matching lines @@
     bool isDocumentNode() const = delete; // This will catch anyone doing an unnecessary check.
 
     void styleAttributeChanged(const AtomicString& newStyleString, AttributeModificationReason);
 
     void updatePresentationAttributeStyle();
 
     void inlineStyleChanged();
     PropertySetCSSStyleDeclaration* inlineStyleCSSOMWrapper();
     void setInlineStyleFromString(const AtomicString&);
 
+    // Returns whether the parent contains independent-only inherited changes
+    // that can be directly propagated to the child.

[meade_UTC10, 2016/07/13 07:29:13]

I found this a little hard to understand - "the child" is this element right?

And this is checking whether the only changed properties are independent (and
thus whether a full style recalc is required)?

[sashab, 2016/07/14 05:08:41]

Yup :) clarified the comment.

+    bool canPropagateInheritedProperties(StyleRecalcChange);
+
     StyleRecalcChange recalcOwnStyle(StyleRecalcChange);
     // TODO(nainar): Make this const ComputedStyle&.
     StyleRecalcChange buildOwnLayout(ComputedStyle&);
 
     inline void checkForEmptyStyleChange();
 
     void updatePseudoElement(PseudoId, StyleRecalcChange);
     bool updateFirstLetter(Element*);
 
     inline void createPseudoElementIfNeeded(PseudoId);
@@ skipping 306 matching lines @@
     static T* create(const QualifiedName&, Document&)
 #define DEFINE_ELEMENT_FACTORY_WITH_TAGNAME(T) \
     T* T::create(const QualifiedName& tagName, Document& document) \
     { \
         return new T(tagName, document); \
     }
 
 } // namespace blink
 
 #endif // Element_h