Expose some sky_viewer plumbing to allow for reuse

sky/viewer/sky_loader.h

Index: sky/viewer/sky_loader.h
diff --git a/sky/viewer/sky_loader.h b/sky/viewer/sky_loader.h
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+// 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_VIEWER_SKY_LOADER_H_
+#define SKY_VIEWER_SKY_LOADER_H_
+
+#include "mojo/public/interfaces/application/shell.mojom.h"
+#include "mojo/services/content_handler/public/interfaces/content_handler.mojom.h"
+#include "mojo/services/network/public/interfaces/network_service.mojom.h"
+
+namespace sky {
+
+// A class that loads Sky applications from URLs.
+class SkyLoader {
+ public:
+  // |shell| must outlive this object.
+  // If |initial_app_to_load| is not null, it will be loaded on the first call
+  // to |LoadApplication()|.
+  SkyLoader(mojo::Shell* shell, mojo::URLResponsePtr initial_app_to_load);
+
+  virtual ~SkyLoader();
+
+  // Loads the application at |url|, passing it |services| and
+  // |exposed_services|.
+  void LoadApplication(mojo::InterfaceRequest<mojo::ServiceProvider> services,
+                       mojo::ServiceProviderPtr exposed_services,
+                       const mojo::String& url);
+
+ private:
+  void OnApplicationLoaded(
+      mojo::URLLoaderPtr loader,
+      mojo::InterfaceRequest<mojo::ServiceProvider> services,
+      mojo::ServiceProviderPtr exposed_services,
+      mojo::URLResponsePtr response);
+
+  mojo::Shell* shell_;
+  mojo::NetworkServicePtr network_service_;
+  mojo::URLResponsePtr initial_app_to_load_;
+};
+
+}  // namespace sky
+
+#endif  // SKY_VIEWER_SKY_LOADER_H_