Revert of Deletes mojo::Callback

mojo/public/cpp/bindings/tests/bindings_perftest.cc

 // 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.
 
 #include <stddef.h>
 #include <utility>
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
@@ skipping 11 matching lines @@
 double MojoTicksToSeconds(MojoTimeTicks ticks) {
   return ticks / kMojoTicksPerSecond;
 }
 
 class PingServiceImpl : public test::PingService {
  public:
   PingServiceImpl() {}
   ~PingServiceImpl() override {}
 
   // |PingService| methods:
-  void Ping(const PingCallback& callback) override;
+  void Ping(const Callback<void()>& callback) override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(PingServiceImpl);
 };
 
-void PingServiceImpl::Ping(const PingCallback& callback) {
+void PingServiceImpl::Ping(const Callback<void()>& callback) {
   callback.Run();
 }
 
 class PingPongTest {
  public:
   explicit PingPongTest(test::PingServicePtr service);
 
   void Run(unsigned int iterations);
 
  private:
@@ skipping 79 matching lines @@
         "InProcessPingPong", "1000_Inactive",
         kIterations / MojoTicksToSeconds(end_time - start_time),
         "pings/second");
 
     delete[] inactive_services;
   }
 }
 
 }  // namespace
 }  // namespace mojo