clang/unittests: Fixup corresponding to r172290.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172295 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/unittests/Lex/LexerTest.cpp b/unittests/Lex/LexerTest.cpp
index 7fca7f4..a7c6284 100644
--- a/unittests/Lex/LexerTest.cpp
+++ b/unittests/Lex/LexerTest.cpp
@@ -59,6 +59,9 @@
                                       bool IsInclusionDirective) {
     return ModuleLoadResult();
   }
+
+  virtual void makeModuleVisible(Module *Mod,
+                                 Module::NameVisibilityKind Visibility) { }
 };
 
 TEST_F(LexerTest, LexAPI) {