Modify bindings to enforce that an error handler callback is only set after binding to a msg pipe.

mojo/public/cpp/bindings/binding.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_CPP_BINDINGS_BINDING_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_BINDING_H_
 
 #include "base/macros.h"
 #include "mojo/public/c/environment/async_waiter.h"
 #include "mojo/public/cpp/bindings/callback.h"
@@ skipping 175 matching lines @@
   // on to associated interface endpoint handles at both sides of the
   // message pipe in order to call this method. We need a way to forcefully
   // invalidate associated interface endpoint handles.
   InterfaceRequest<Interface> Unbind() {
     CHECK(!HasAssociatedInterfaces());
     return internal_state_.Unbind();
   }
 
   // Sets an error handler that will be called if a connection error occurs on
   // the bound message pipe.
+  //
+  // 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 Closure& error_handler) {
+    DCHECK(is_bound());
     internal_state_.set_connection_error_handler(error_handler);
   }
 
   // Returns the interface implementation that was previously specified. Caller
   // does not take ownership.
   Interface* impl() { return internal_state_.impl(); }
 
   // Indicates whether the binding has been completed (i.e., whether a message
   // pipe has been bound to the implementation).
   bool is_bound() const { return internal_state_.is_bound(); }
@@ skipping 18 matching lines @@
  private:
   internal::BindingState<Interface, Interface::PassesAssociatedKinds_>
       internal_state_;
 
   DISALLOW_COPY_AND_ASSIGN(Binding);
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_BINDING_H_