Remove all remaining HashMap and HashSet usages except dart_string_cache

sky/engine/tonic/dart_dependency_catcher.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 SKY_ENGINE_TONIC_DART_DEPENDENCY_CATCHER_H_
 #define SKY_ENGINE_TONIC_DART_DEPENDENCY_CATCHER_H_
 
+#include <unordered_set>
+
 #include "base/macros.h"
-#include "sky/engine/wtf/HashSet.h"
 
 namespace blink {
 class DartLibraryLoader;
 
 // A base class to represent a dependency.
 class DartDependency {};
 
 // To catch the dependencies for a library, put a DartDependencyCatcher on the
 // stack during the call to Dart_LoadLibrary.
 class DartDependencyCatcher {
  public:
   explicit DartDependencyCatcher(DartLibraryLoader& loader);
   ~DartDependencyCatcher();
 
   void AddDependency(DartDependency* dependency);
-  const HashSet<DartDependency*>& dependencies() const { return dependencies_; }
+  const std::unordered_set<DartDependency*>& dependencies() const {
+    return dependencies_;
+  }
 
  private:
   DartLibraryLoader& loader_;
-  HashSet<DartDependency*> dependencies_;
+  std::unordered_set<DartDependency*> dependencies_;
 
   DISALLOW_COPY_AND_ASSIGN(DartDependencyCatcher);
 };
 
 }  // namespace blink
 
 #endif  // SKY_ENGINE_TONIC_DART_DEPENDENCY_CATCHER_H_