Add a new SBThread::SafeToCallFunctions API; this calls over to

the SystemRuntime to check if a thread will have any problems 
performing an inferior function call so the driver can skip
making that function call on that thread.  Often the function
call can be executed on another thread instead.
<rdar://problem/16777874> 

llvm-svn: 208732

lldb/source/API/SBThread.cpp

@@ -1437,3 +1437,12 @@ SBThread::GetExtendedBacktraceOriginatingIndexID ()
         return thread_sp->GetExtendedBacktraceOriginatingIndexID();
     return LLDB_INVALID_INDEX32;
 }
+
+bool
+SBThread::SafeToCallFunctions ()
+{
+    ThreadSP thread_sp(m_opaque_sp->GetThreadSP());
+    if (thread_sp)
+        return thread_sp->SafeToCallFunctions();
+    return true;
+}