Dart: Reorganize files

mojo/dart/embedder/snapshotter/vm.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 MOJO_DART_DART_SNAPSHOTTER_VM_H_
-#define MOJO_DART_DART_SNAPSHOTTER_VM_H_
+#ifndef MOJO_DART_EMBEDDER_SNAPSHOTTER_VM_H_
+#define MOJO_DART_EMBEDDER_SNAPSHOTTER_VM_H_
 
 #include "dart/runtime/include/dart_api.h"
 #include "tonic/dart_library_provider.h"
 #include "tonic/dart_state.h"
 
 class SnapshotterDartState : public tonic::DartState {
  public:
   SnapshotterDartState() : library_provider_(nullptr) {
   };
 
@@ skipping 18 matching lines @@
     return reinterpret_cast<SnapshotterDartState*>(data);
   }
 
  private:
   std::unique_ptr<tonic::DartLibraryProvider> library_provider_;
 };
 
 void InitDartVM();
 Dart_Isolate CreateDartIsolate();
 
-#endif  // MOJO_DART_DART_SNAPSHOTTER_VM_H_
+#endif  // MOJO_DART_EMBEDDER_SNAPSHOTTER_VM_H_