Helium: Initial proto and Syncable interface definition

blimp/common/mandatory_callback.h

 // Copyright 2016 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 BLIMP_COMMON_MANDATORY_CALLBACK_H_
 #define BLIMP_COMMON_MANDATORY_CALLBACK_H_
 
 #include <utility>
 
 #include "base/callback.h"
@@ skipping 50 matching lines @@
     other.was_run_ = false;
 #endif
   }
 
   ~MandatoryCallback() {
 #if DCHECK_IS_ON()
     DCHECK(cb_.is_null() || was_run_);
 #endif
   }
 
+  // This a overload that handles the case where there are no arguments provided
+  template <typename...>
+  ReturnType Run() {
+    DCHECK(cb_);  // Can't be run following std::move.
+
+#if DCHECK_IS_ON()
+    DCHECK(!was_run_);
+    was_run_ = true;
+#endif
+
+    cb_.Run();
+  }
+
   template <typename... RunArgs>
   ReturnType Run(RunArgs... args) {
     DCHECK(cb_);  // Can't be run following std::move.
 
 #if DCHECK_IS_ON()
     DCHECK(!was_run_);
     was_run_ = true;
 #endif
 
     cb_.Run(std::forward<RunArgs...>(args...));
@@ skipping 10 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(MandatoryCallback);
 };
 
 // Creates a leak-checking proxy callback around |callback|.
 template <typename SignatureType>
 MandatoryCallback<SignatureType> CreateMandatoryCallback(
     const base::Callback<SignatureType>& callback) {
   return MandatoryCallback<SignatureType>(callback);
 }
 
+using MandatoryClosure = MandatoryCallback<void()>;
+
 }  // namespace blimp
 
 #endif  // BLIMP_COMMON_MANDATORY_CALLBACK_H_