CXXThisScopeRAII objects aren't free, don't compute one if it's unused.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@156987 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Parse/ParseDecl.cpp b/lib/Parse/ParseDecl.cpp
index d135010..c3ffd9e 100644
--- a/lib/Parse/ParseDecl.cpp
+++ b/lib/Parse/ParseDecl.cpp
@@ -742,7 +742,7 @@
   if (!AlreadyHasClassScope)
     Actions.ActOnStartDelayedMemberDeclarations(getCurScope(),
                                                 Class.TagOrTemplate);
-  {
+  if (!Class.LateParsedDeclarations.empty()) {
     // Allow 'this' within late-parsed attributes.
     Sema::CXXThisScopeRAII ThisScope(Actions, Class.TagOrTemplate, 
                                      /*TypeQuals=*/0);