Pass ServiceProvider thru ViewManagerService::Embed() allowing embedder & embeddee to expose servic…

mojo/public/cpp/application/lib/weak_service_provider.h

+// Copyright 2014 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_PUBLIC_APPLICATION_LIB_WEAK_SERVICE_PROVIDER_H_
+#define MOJO_PUBLIC_APPLICATION_LIB_WEAK_SERVICE_PROVIDER_H_
+
+#include "mojo/public/interfaces/application/service_provider.mojom.h"
+
+namespace mojo {
+namespace internal {
+class ServiceConnectorBase;
+
+// Implements a weak pointer to a ServiceProvider. Necessary as the lifetime of
+// the ServiceProviderImpl is bound to that of its pipe, but code may continue
+// to reference a remote service provider beyond the lifetime of said pipe.
+// Calls to ConnectToService() are silently dropped when the pipe is closed.
+class WeakServiceProvider : public ServiceProvider {
+ public:
+  explicit WeakServiceProvider(ServiceProvider* service_provider);
+  virtual ~WeakServiceProvider();
+
+  void Clear();
+
+ private:
+  // Overridden from ServiceProvider:
+  virtual void ConnectToService(
+      const String& service_name,
+      ScopedMessagePipeHandle client_handle) MOJO_OVERRIDE;
+
+  ServiceProvider* service_provider_;
+
+  MOJO_DISALLOW_COPY_AND_ASSIGN(WeakServiceProvider);
+};
+
+}  // namespace internal
+}  // namespace mojo
+
+#endif  // MOJO_PUBLIC_APPLICATION_LIB_WEAK_SERVICE_PROVIDER_H_