Don't crash in SendBuildID when MessageChannel isn't connected. (bug 1333056, r=dvander)

xpcshell can sometimes create and then almost immediately kill the GPU process. This can
cause the connection state of GPUParent's message channel to be in error or closed
when it attempts to send its build ID. In this case we should ignore the request
because the process will soon close.

MozReview-Commit-ID: EAupU844iFo

--HG--
extra : histedit_source : df05a01df5ad095b4e3c91e0e038d4e145da5f9d

ipc/glue/MessageChannel.cpp

@@ -1018,7 +1018,7 @@ MessageChannel::SendBuildID()
     MonitorAutoLock lock(*mMonitor);
     if (!Connected()) {
         ReportConnectionError("MessageChannel", msg);
-        MOZ_CRASH();
+        return;
     }
     mLink->SendMessage(msg.forget());
 }