Add a test case for r128957. It fixed a bug!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@128966 91177308-0d34-0410-b5e6-96231b3b80d8

test/CodeGenCXX/debug-info-this.cpp

@@ -0,0 +1,15 @@
+// RUN: %clang -emit-llvm -g -S %s -o - | FileCheck %s
+// Radar 9239104
+class Class
+{
+public:
+//CHECK: DW_TAG_const_type
+    int foo (int p) const {
+        return p+m_int;
+    }  
+
+protected:
+    int m_int;
+};
+
+Class c;