--- a/ipc/chromium/src/base/message_loop.cc
+++ b/ipc/chromium/src/base/message_loop.cc
@@ -120,16 +120,19 @@ MessageLoop::MessageLoop(Type type)
   case TYPE_MOZILLA_NONMAINTHREAD:
     pump_ = new mozilla::ipc::MessagePumpForNonMainThreads();
     return;
 #if defined(OS_WIN)
   case TYPE_MOZILLA_NONMAINUITHREAD:
     pump_ = new mozilla::ipc::MessagePumpForNonMainUIThreads();
     return;
 #endif
+  default:
+    // Create one of Chromium's standard MessageLoop types below.
+    break;
   }
 
 #if defined(OS_WIN)
   // TODO(rvargas): Get rid of the OS guards.
   if (type_ == TYPE_DEFAULT) {
     pump_ = new base::MessagePumpDefault();
   } else if (type_ == TYPE_IO) {
     pump_ = new base::MessagePumpForIO();