Port more String and HashMap usages

sky/engine/tonic/dart_snapshot_loader.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_SNAPSHOT_LOADER_H_
 #define SKY_ENGINE_TONIC_DART_SNAPSHOT_LOADER_H_
 
 #include <vector>
 
 #include "base/callback_forward.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "dart/runtime/include/dart_api.h"
 #include "mojo/common/data_pipe_drainer.h"
 #include "sky/engine/wtf/OwnPtr.h"
-#include "sky/engine/wtf/text/WTFString.h"
 
 namespace blink {
 class DartState;
 
 class DartSnapshotLoader : public mojo::common::DataPipeDrainer::Client {
  public:
   explicit DartSnapshotLoader(DartState* dart_state);
   ~DartSnapshotLoader();
 
   void LoadSnapshot(mojo::ScopedDataPipeConsumerHandle pipe,
                     const base::Closure& callback);
 
  private:
   // mojo::common::DataPipeDrainer::Client
   void OnDataAvailable(const void* data, size_t num_bytes) override;
   void OnDataComplete() override;
 
   base::WeakPtr<DartState> dart_state_;
   OwnPtr<mojo::common::DataPipeDrainer> drainer_;
   // TODO(abarth): Should we be using SharedBuffer to buffer the data?
   std::vector<uint8_t> buffer_;
   base::Closure callback_;
 
   DISALLOW_COPY_AND_ASSIGN(DartSnapshotLoader);
 };
 
 }  // namespace blink
 
 #endif  // SKY_ENGINE_TONIC_DART_SNAPSHOT_LOADER_H_