Make LLDB skip server-client roundtrip for signals that don't require any actions

If QPassSignals packaet is supported by lldb-server, lldb-client will
utilize it and ask the server to ignore signals that don't require stops
or notifications.
Such signals will be immediately re-injected into inferior to continue
normal execution.

Differential Revision: https://reviews.llvm.org/D30520

llvm-svn: 297231
diff --git a/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.h b/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.h
index bb00af8..ec8827a 100644
--- a/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.h
+++ b/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.h
@@ -397,12 +397,15 @@
                                      lldb::addr_t base_addr,
                                      bool value_is_offset);
 
+  Error UpdateAutomaticSignalFiltering() override;
+
 private:
   //------------------------------------------------------------------
   // For ProcessGDBRemote only
   //------------------------------------------------------------------
   std::string m_partial_profile_data;
   std::map<uint64_t, uint32_t> m_thread_id_to_used_usec_map;
+  uint64_t m_last_signals_version = 0;
 
   static bool NewThreadNotifyBreakpointHit(void *baton,
                                            StoppointCallbackContext *context,