Have HashMap<KeyType, AtomicString>::get() return a const reference

Source/core/timing/Performance.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2012 Intel Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 149 matching lines @@
 }
 
 static bool passesTimingAllowCheck(const ResourceResponse& response, Document* requestingDocument)
 {
     AtomicallyInitializedStatic(AtomicString&, timingAllowOrigin = *new AtomicString("timing-allow-origin"));
 
     RefPtr<SecurityOrigin> resourceOrigin = SecurityOrigin::create(response.url());
     if (resourceOrigin->isSameSchemeHostPort(requestingDocument->securityOrigin()))
         return true;
 
-    const String& timingAllowOriginString = response.httpHeaderField(timingAllowOrigin);
+    const AtomicString& timingAllowOriginString = response.httpHeaderField(timingAllowOrigin);
     if (timingAllowOriginString.isEmpty() || equalIgnoringCase(timingAllowOriginString, "null"))
         return false;
 
     if (timingAllowOriginString == "*")
         return true;
 
     const String& securityOrigin = requestingDocument->securityOrigin()->toString();
     Vector<String> timingAllowOrigins;
-    timingAllowOriginString.split(" ", timingAllowOrigins);
+    timingAllowOriginString.string().split(" ", timingAllowOrigins);
     for (size_t i = 0; i < timingAllowOrigins.size(); ++i) {
         if (timingAllowOrigins[i] == securityOrigin)
             return true;
     }
 
     return false;
 }
 
 static bool allowsTimingRedirect(const Vector<ResourceResponse>& redirectChain, const ResourceResponse& finalResponse, Document* initiatorDocument)
 {
@@ skipping 81 matching lines @@
         m_userTiming = UserTiming::create(this);
     m_userTiming->clearMeasures(measureName);
 }
 
 double Performance::now() const
 {
     return 1000.0 * (monotonicallyIncreasingTime() - m_referenceTime);
 }
 
 } // namespace WebCore