Be sure to take the mutex when the destructor is called in case other threads are using these lists and those other threads have the mutex locked.

llvm-svn: 178262
diff --git a/lldb/source/Target/StackFrameList.cpp b/lldb/source/Target/StackFrameList.cpp
index d9d5544..39aa1bc 100644
--- a/lldb/source/Target/StackFrameList.cpp
+++ b/lldb/source/Target/StackFrameList.cpp
@@ -65,6 +65,9 @@
 //----------------------------------------------------------------------
 StackFrameList::~StackFrameList()
 {
+    // Call clear since this takes a lock and clears the stack frame list
+    // in case another thread is currently using this stack frame list
+    Clear();
 }
 
 void