Mojo C++ bindings: fix [D]CHECKs in MultiplexRouter and SyncHandleRegistry.

mojo/public/cpp/bindings/lib/multiplex_router.cc

Index: mojo/public/cpp/bindings/lib/multiplex_router.cc
diff --git a/mojo/public/cpp/bindings/lib/multiplex_router.cc b/mojo/public/cpp/bindings/lib/multiplex_router.cc
index 5602b2a0591e6d9fc26f2f386bad76f3dab823d0..14ea64740756a9377829c23512a2eb1b7b457603 100644
--- a/mojo/public/cpp/bindings/lib/multiplex_router.cc
+++ b/mojo/public/cpp/bindings/lib/multiplex_router.cc
@@ -335,8 +335,16 @@ MultiplexRouter::~MultiplexRouter() {
     // because it may remove the corresponding value from the map.
     ++iter;
 
-    DCHECK(endpoint->closed());
-    UpdateEndpointStateMayRemove(endpoint, PEER_ENDPOINT_CLOSED);
+    if (!endpoint->closed()) {
+      // This happens when a NotifyPeerEndpointClosed message been received, but
+      // (1) the interface ID hasn't been used to create local endpoint handle;
+      // and (2) a NotifyEndpointClosedBeforeSent hasn't been received.
+      DCHECK(!endpoint->client());
+      DCHECK(endpoint->peer_closed());
+      UpdateEndpointStateMayRemove(endpoint, ENDPOINT_CLOSED);
+    } else {
+      UpdateEndpointStateMayRemove(endpoint, PEER_ENDPOINT_CLOSED);
+    }
   }
 
   DCHECK(endpoints_.empty());