second pass over removal of Mutex and Condition

llvm-svn: 270024
diff --git a/lldb/source/Symbol/DWARFCallFrameInfo.cpp b/lldb/source/Symbol/DWARFCallFrameInfo.cpp
index e594bd5..a319430 100644
--- a/lldb/source/Symbol/DWARFCallFrameInfo.cpp
+++ b/lldb/source/Symbol/DWARFCallFrameInfo.cpp
@@ -308,9 +308,9 @@
     
     if (m_fde_index_initialized)
         return;
-    
-    Mutex::Locker locker(m_fde_index_mutex);
-    
+
+    std::lock_guard<std::mutex> guard(m_fde_index_mutex);
+
     if (m_fde_index_initialized) // if two threads hit the locker
         return;