Temporarily roll back the parts of r211241 where I fixed a
mistake in the lock acquistion in HistoryUnwind and HistoryThread.
We've got a deadlock with one use case of HistoryUnwind; I
need to figure out what lock ordering is causing this and fix
it for real.  
<rdar://problem/17411904> 

llvm-svn: 211541
diff --git a/lldb/source/Plugins/Process/Utility/HistoryUnwind.cpp b/lldb/source/Plugins/Process/Utility/HistoryUnwind.cpp
index bf8b3f5..f809ebe 100644
--- a/lldb/source/Plugins/Process/Utility/HistoryUnwind.cpp
+++ b/lldb/source/Plugins/Process/Utility/HistoryUnwind.cpp
@@ -66,7 +66,7 @@
 bool
 HistoryUnwind::DoGetFrameInfoAtIndex (uint32_t frame_idx, lldb::addr_t& cfa, lldb::addr_t& pc)
 {
-    Mutex::Locker locker(m_unwind_mutex);
+    Mutex::Locker (m_unwind_mutex);   // FIXME do not throw away the lock after we acquire it..
     if (frame_idx < m_pcs.size())
     {
         cfa = frame_idx;