Remove dead code from DartController

sky/engine/core/script/dart_library_provider_webview.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_CORE_SCRIPT_DART_LIBRARY_PROVIDER_WEBVIEW_H_
-#define SKY_ENGINE_CORE_SCRIPT_DART_LIBRARY_PROVIDER_WEBVIEW_H_
-
-#include "sky/engine/tonic/dart_library_provider.h"
-#include "sky/engine/wtf/HashSet.h"
-#include "sky/engine/wtf/OwnPtr.h"
-
-namespace blink {
-
-class DartLibraryProviderWebView : public DartLibraryProvider {
- public:
-  explicit DartLibraryProviderWebView();
-  ~DartLibraryProviderWebView() override;
-
- private:
-  class Job;
-
-  // |DartLibraryProvider| implementation:
-  void GetLibraryAsStream(
-      const String& name,
-      DataPipeConsumerCallback callback)
-      override;
-
-  Dart_Handle CanonicalizeURL(Dart_Handle library, Dart_Handle url) override;
-
-  HashSet<OwnPtr<Job>> jobs_;
-};
-
-}  // namespace blink
-
-#endif  // SKY_ENGINE_CORE_SCRIPT_DART_LIBRARY_PROVIDER_WEBVIEW_H_