Remove the MessageLoop::DestructionObserver from mojo bindings.

mojo/public/cpp/bindings/strong_binding.h

Index: mojo/public/cpp/bindings/strong_binding.h
diff --git a/mojo/public/cpp/bindings/strong_binding.h b/mojo/public/cpp/bindings/strong_binding.h
index 07f0c164d82d7fb2fd1caa30b02ca167534d8fdb..f4b4a061cd9290955fa94a48f21771bde22267ab 100644
--- a/mojo/public/cpp/bindings/strong_binding.h
+++ b/mojo/public/cpp/bindings/strong_binding.h
@@ -31,7 +31,9 @@ template <typename Interface>
 using StrongBindingPtr = base::WeakPtr<StrongBinding<Interface>>;
 
 // This connects an interface implementation strongly to a pipe. When a
-// connection error is detected the implementation is deleted.
+// connection error is detected the implementation is deleted. If the task
+// runner that a StrongBinding is bound on is stopped, the connection error
+// handler will not be invoked and the implementation will not be deleted.
 //
 // To use, call StrongBinding<T>::Create() (see below) or the helper
 // MakeStrongBinding function: