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 cbab4238a125f9a8e629cb2050438059b60e5c97..5c5243ca2145f76bcc21b0e268d3a483ab44d981 100644
--- a/mojo/public/cpp/bindings/interface_endpoint_client.h
+++ b/mojo/public/cpp/bindings/interface_endpoint_client.h
@@ -16,7 +16,6 @@
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
-#include "base/message_loop/message_loop.h"
 #include "base/optional.h"
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread_checker.h"
@@ -39,8 +38,7 @@ 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.
@@ -153,10 +151,6 @@ 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_;
@@ -180,8 +174,6 @@ 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_;