Remove some HashMap

sky/engine/tonic/dart_class_library.h

Index: sky/engine/tonic/dart_class_library.h
diff --git a/sky/engine/tonic/dart_class_library.h b/sky/engine/tonic/dart_class_library.h
index 5a1b2125d86e2b0837ca64a9fd99b1da8aa799ab..05b75e1388b75090c1da875ad0eacab4f81451ec 100644
--- a/sky/engine/tonic/dart_class_library.h
+++ b/sky/engine/tonic/dart_class_library.h
@@ -5,10 +5,10 @@
 #ifndef SKY_ENGINE_TONIC_DART_CLASS_LIBRARY_H_
 #define SKY_ENGINE_TONIC_DART_CLASS_LIBRARY_H_
 
+#include <unordered_map>
 #include "base/macros.h"
 #include "dart/runtime/include/dart_api.h"
 #include "sky/engine/tonic/dart_class_provider.h"
-#include "sky/engine/wtf/HashMap.h"
 
 namespace blink {
 struct DartWrapperInfo;
@@ -23,7 +23,7 @@ class DartClassLibrary {
 
  private:
   DartClassProvider* provider_;
-  HashMap<const DartWrapperInfo*, Dart_PersistentHandle> cache_;
+  std::unordered_map<const DartWrapperInfo*, Dart_PersistentHandle> cache_;
 
   DISALLOW_COPY_AND_ASSIGN(DartClassLibrary);
 };