Ensure string data is kept alive as long as there are CSSVariableData tokens pointing to it

third_party/WebKit/Source/core/css/resolver/CSSVariableResolver.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CSSVariableResolver_h
 #define CSSVariableResolver_h
 
 #include "core/CSSPropertyNames.h"
 #include "core/css/parser/CSSParserToken.h"
 #include "platform/wtf/HashSet.h"
@@ skipping 40 matching lines @@
       const CSSVariableReferenceValue&,
       bool disallow_animation_tainted);
 
   // These return false if we encounter a reference to an invalid variable with
   // no fallback.
 
   // Resolves a range which may contain var() references or @apply rules.
   bool ResolveTokenRange(CSSParserTokenRange,
                          bool disallow_animation_tainted,
                          Vector<CSSParserToken>& result,
+                         Vector<String>& result_backing_strings,
                          bool& result_is_animation_tainted);
   // Resolves the fallback (if present) of a var() reference, starting from the
   // comma.
   bool ResolveFallback(CSSParserTokenRange,
                        bool disallow_animation_tainted,
                        Vector<CSSParserToken>& result,
+                       Vector<String>& result_backing_strings,
                        bool& result_is_animation_tainted);
   // Resolves the contents of a var() reference.
   bool ResolveVariableReference(CSSParserTokenRange,
                                 bool disallow_animation_tainted,
                                 Vector<CSSParserToken>& result,
+                                Vector<String>& result_backing_strings,
                                 bool& result_is_animation_tainted);
   // Consumes and resolves an @apply rule.
-  void ResolveApplyAtRule(CSSParserTokenRange&, Vector<CSSParserToken>& result);
+  void ResolveApplyAtRule(CSSParserTokenRange&,
+                          Vector<CSSParserToken>& result,
+                          Vector<String>& result_backing_strings);
 
   // These return null if the custom property is invalid.
 
   // Returns the CSSVariableData for a custom property, resolving and storing it
   // if necessary.
   CSSVariableData* ValueForCustomProperty(AtomicString name);
   // Resolves the CSSVariableData from a custom property declaration.
   PassRefPtr<CSSVariableData> ResolveCustomProperty(AtomicString name,
                                                     const CSSVariableData&);
 
   StyleInheritedVariables* inherited_variables_;
   StyleNonInheritedVariables* non_inherited_variables_;
   Member<const PropertyRegistry> registry_;
   HashSet<AtomicString> variables_seen_;
   // Resolution doesn't finish when a cycle is detected. Fallbacks still
   // need to be tracked for additional cycles, and invalidation only
   // applies back to cycle starts.
   HashSet<AtomicString> cycle_start_points_;
 };
 
 }  // namespace blink
 
 #endif  // CSSVariableResolver