Add fast-path for propagated variable changes (WIP)

third_party/WebKit/Source/core/css/resolver/StyleBuilderCustom.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc.
  * All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
@@ skipping 102 matching lines @@
                                  StyleResolverState& state,
                                  const CSSValue& value) {
   if (id != CSSPropertyVariable && (value.isVariableReferenceValue() ||
                                     value.isPendingSubstitutionValue())) {
     bool omitAnimationTainted = CSSAnimations::isAnimationAffectingProperty(id);
     const CSSValue* resolvedValue =
         CSSVariableResolver::resolveVariableReferences(state, id, value,
                                                        omitAnimationTainted);
     applyProperty(id, state, *resolvedValue);
 
-    if (!state.style()->hasVariableReferenceFromNonInheritedProperty() &&
-        !CSSPropertyMetadata::isInheritedProperty(id))
+    // TODO(sashab): Clear this flag if all properties are set back to
+    // non-variable references.
+    if (CSSPropertyMetadata::isInheritedProperty(id))
+      state.style()->setHasVariableReferenceFromInheritedProperty();
+    else
       state.style()->setHasVariableReferenceFromNonInheritedProperty();
+
     return;
   }
 
   DCHECK(!isShorthandProperty(id)) << "Shorthand property id = " << id
                                    << " wasn't expanded at parsing time";
 
   bool isInherit = state.parentNode() && value.isInheritedValue();
   bool isInitial = value.isInitialValue() ||
                    (!state.parentNode() && value.isInheritedValue());
 
@@ skipping 896 matching lines @@
   }
 }
 
 void StyleBuilderFunctions::applyInheritCSSPropertyPosition(
     StyleResolverState& state) {
   if (!state.parentNode()->isDocumentNode())
     state.style()->setPosition(state.parentStyle()->position());
 }
 
 }  // namespace blink