Add initial --extended / -e support to thread backtrace.

llvm-svn: 194455
diff --git a/lldb/source/Target/SystemRuntime.cpp b/lldb/source/Target/SystemRuntime.cpp
index 7ce150f..c885aa7 100644
--- a/lldb/source/Target/SystemRuntime.cpp
+++ b/lldb/source/Target/SystemRuntime.cpp
@@ -33,7 +33,8 @@
 // SystemRuntime constructor
 //----------------------------------------------------------------------
 SystemRuntime::SystemRuntime(Process *process) :
-    m_process (process)
+    m_process (process),
+    m_types ()
 {
 }
 
@@ -59,11 +60,10 @@
 {
 }
 
-std::vector<ConstString>
+const std::vector<ConstString> &
 SystemRuntime::GetExtendedBacktraceTypes ()
 {
-    std::vector<ConstString> types;
-    return types;
+    return m_types;
 }
 
 ThreadSP