Revert of Deletes mojo::Callback

mojo/public/cpp/bindings/binding.h

Index: mojo/public/cpp/bindings/binding.h
diff --git a/mojo/public/cpp/bindings/binding.h b/mojo/public/cpp/bindings/binding.h
index 8c9ee2f0c5292c9eaa0d5f534cc3352d0eed9aee..84b4f90d62d451fa9b4511ae039cffa6375a3989 100644
--- a/mojo/public/cpp/bindings/binding.h
+++ b/mojo/public/cpp/bindings/binding.h
@@ -7,11 +7,11 @@
 
 #include <utility>
 
-#include "base/callback_forward.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
+#include "mojo/public/cpp/bindings/callback.h"
 #include "mojo/public/cpp/bindings/interface_ptr.h"
 #include "mojo/public/cpp/bindings/interface_ptr_info.h"
 #include "mojo/public/cpp/bindings/interface_request.h"
@@ -212,7 +212,7 @@
   // This method may only be called after this Binding has been bound to a
   // message pipe. The error handler will be reset when this Binding is unbound
   // or closed.
-  void set_connection_error_handler(const base::Closure& error_handler) {
+  void set_connection_error_handler(const Closure& error_handler) {
     DCHECK(is_bound());
     internal_state_.set_connection_error_handler(error_handler);
   }