Remove the MessageLoop::DestructionObserver from mojo bindings.

mojo/public/cpp/bindings/interface_endpoint_client.h

Index: mojo/public/cpp/bindings/interface_endpoint_client.h
diff --git a/mojo/public/cpp/bindings/interface_endpoint_client.h b/mojo/public/cpp/bindings/interface_endpoint_client.h
index 6129d75bbf7511716d6a511bfaa5fa67a972b47d..da5df227160fc660a3b39bee1deae78ba09e87fd 100644
--- a/mojo/public/cpp/bindings/interface_endpoint_client.h
+++ b/mojo/public/cpp/bindings/interface_endpoint_client.h
@@ -37,8 +37,7 @@ class InterfaceEndpointController;
 // endpoint, either the implementation side or the client side.
 // It should only be accessed and destructed on the creating thread.
 class MOJO_CPP_BINDINGS_EXPORT InterfaceEndpointClient
-    : NON_EXPORTED_BASE(public MessageReceiverWithResponder),
-      public base::MessageLoop::DestructionObserver {
+    : NON_EXPORTED_BASE(public MessageReceiverWithResponder) {
  public:
   // |receiver| is okay to be null. If it is not null, it must outlive this
   // object.
@@ -149,10 +148,6 @@ class MOJO_CPP_BINDINGS_EXPORT InterfaceEndpointClient
   };
 
   bool HandleValidatedMessage(Message* message);
-  void StopObservingIfNecessary();
-
-  // base::MessageLoop::DestructionObserver:
-  void WillDestroyCurrentMessageLoop() override;
 
   ScopedInterfaceEndpointHandle handle_;
   std::unique_ptr<AssociatedGroup> associated_group_;
@@ -176,8 +171,6 @@ class MOJO_CPP_BINDINGS_EXPORT InterfaceEndpointClient
   internal::ControlMessageProxy control_message_proxy_;
   internal::ControlMessageHandler control_message_handler_;
 
-  bool observing_message_loop_destruction_ = true;
-
   base::ThreadChecker thread_checker_;
 
   base::WeakPtrFactory<InterfaceEndpointClient> weak_ptr_factory_;