Factor DartLibraryProvider out of DartLoader

sky/engine/tonic/dart_library_provider.h

Index: sky/engine/tonic/dart_library_provider.h
diff --git a/sky/engine/tonic/dart_library_provider.h b/sky/engine/tonic/dart_library_provider.h
new file mode 100644
index 0000000000000000000000000000000000000000..737e673771cf0cd71549b9728f6cd82a7ae361d0
--- /dev/null
+++ b/sky/engine/tonic/dart_library_provider.h
@@ -0,0 +1,29 @@
+// 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_LIBRARY_PROVIDER_H_
+#define SKY_ENGINE_TONIC_DART_LIBRARY_PROVIDER_H_
+
+#include "base/callback.h"
+#include "dart/runtime/include/dart_api.h"
+#include "mojo/public/cpp/system/data_pipe.h"
+#include "sky/engine/wtf/text/WTFString.h"
+
+namespace blink {
+
+class DartLibraryProvider {
+ public:
+  virtual void GetLibraryAsStream(
+      const String& name,
+      base::Callback<void(mojo::ScopedDataPipeConsumerHandle)> callback) = 0;
+
+  virtual Dart_Handle CanonicalizeURL(Dart_Handle library, Dart_Handle url) = 0;
+
+ protected:
+  virtual ~DartLibraryProvider();
+};
+
+}  // namespace blink
+
+#endif  // SKY_ENGINE_TONIC_DART_LIBRARY_PROVIDER_H_