Migrate WTF::HashMap::get() to ::at()

third_party/WebKit/Source/core/xml/XPathVariableReference.cpp

 /*
  * Copyright 2005 Frerich Raabe <raabe@kde.org>
  * Copyright (C) 2006 Apple Computer, Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 22 matching lines @@
 
 VariableReference::VariableReference(const String& name) : m_name(name) {}
 
 Value VariableReference::evaluate(EvaluationContext& context) const {
   HashMap<String, String>& bindings = context.variableBindings;
   if (!bindings.contains(m_name)) {
     // FIXME: Is this the right thing to do if an unknown variable is
     // referenced?
     return "";
   }
-  return bindings.get(m_name);
+  return bindings.at(m_name);
 }
 
 }  // namespace XPath
 }  // namespace blink