Plumb MojoReplaceHandleWithReducedRights() out.

mojo/public/platform/native/system_thunks.h

Index: mojo/public/platform/native/system_thunks.h
diff --git a/mojo/public/platform/native/system_thunks.h b/mojo/public/platform/native/system_thunks.h
index 3650d1f6c8de47def676306866e02457b364a99e..03f2ccbe91b7d2918aaadce9e637d2c6c92df0bb 100644
--- a/mojo/public/platform/native/system_thunks.h
+++ b/mojo/public/platform/native/system_thunks.h
@@ -132,6 +132,10 @@ struct MojoSystemThunks {
       MojoHandleRights rights_to_remove,
       MojoHandle* new_handle);
   MojoResult (*DuplicateHandle)(MojoHandle handle, MojoHandle* new_handle);
+  MojoResult (*ReplaceHandleWithReducedRights)(
+      MojoHandle handle,
+      MojoHandleRights rights_to_remove,
+      MojoHandle* replacement_handle);
 };
 #pragma pack(pop)
 
@@ -168,6 +172,7 @@ inline MojoSystemThunks MojoMakeSystemThunks() {
       MojoGetRights,
       MojoDuplicateHandleWithReducedRights,
       MojoDuplicateHandle,
+      MojoReplaceHandleWithReducedRights,
   };
   return system_thunks;
 }