EDK: Add MojoHandleRights to DispatcherTransport.

mojo/edk/system/handle.h

Index: mojo/edk/system/handle.h
diff --git a/mojo/edk/system/handle.h b/mojo/edk/system/handle.h
index 458e0933146d1b6c2ac40a8a1b8fdaebfda12a80..62218ceb21772208b3a7f8374025b98ebc1ebfb2 100644
--- a/mojo/edk/system/handle.h
+++ b/mojo/edk/system/handle.h
@@ -33,6 +33,8 @@ struct Handle {
   // A |Handle| tests as true if it actually has a dispatcher.
   explicit operator bool() const { return !!dispatcher; }
 
+  void reset() { *this = Handle(); }
+
   // Note: |dispatcher| is guaranteed to be null if default-constructed or
   // moved-from, but we make no guarantees about the value of |rights| in either
   // case.