DCHECK style is cacheable in ComputedStyle::CopyNonInheritedFromCached.

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

 /*
  * 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.
  * (http://www.torchmobile.com/)
@@ skipping 99 matching lines @@
 void MatchedPropertiesCache::ClearViewportDependent() {
   Vector<unsigned, 16> to_remove;
   for (const auto& cache_entry : cache_) {
     CachedMatchedProperties* cache_item = cache_entry.value.Get();
     if (cache_item->computed_style->HasViewportUnits())
       to_remove.push_back(cache_entry.key);
   }
   cache_.RemoveAll(to_remove);
 }
 
+bool MatchedPropertiesCache::IsStyleCacheable(const ComputedStyle& style) {
+  // unique() styles are not cacheable.
+  if (style.Unique())
+    return false;
+  if (style.Zoom() != ComputedStyle::InitialZoom())
+    return false;
+  if (style.GetWritingMode() != ComputedStyle::InitialWritingMode() ||
+      style.Direction() != ComputedStyle::InitialDirection())
+    return false;
+  // styles with non inherited properties that reference variables are not
+  // cacheable.
+  if (style.HasVariableReferenceFromNonInheritedProperty())
+    return false;
+  return true;
+}
+
 bool MatchedPropertiesCache::IsCacheable(const StyleResolverState& state) {
   const ComputedStyle& style = *state.Style();
   const ComputedStyle& parent_style = *state.ParentStyle();
 
-  if (style.Unique() ||
-      (style.StyleType() != kPseudoIdNone && parent_style.Unique()))
+  if (!IsStyleCacheable(style))
     return false;
-  if (style.Zoom() != ComputedStyle::InitialZoom())
-    return false;
-  if (style.GetWritingMode() != ComputedStyle::InitialWritingMode() ||
-      style.Direction() != ComputedStyle::InitialDirection())
+  if (style.StyleType() != kPseudoIdNone && parent_style.Unique())
     return false;
   // The cache assumes static knowledge about which properties are inherited.
   // Without a flat tree parent, StyleBuilder::ApplyProperty will not
   // SetHasExplicitlyInheritedProperties on the parent style.
   if (!state.ParentNode() || parent_style.HasExplicitlyInheritedProperties())
     return false;
-  if (style.HasVariableReferenceFromNonInheritedProperty())
-    return false;
   return true;
 }
 
 DEFINE_TRACE(MatchedPropertiesCache) {
   visitor->Trace(cache_);
 }
 
 }  // namespace blink