Initialize member.

llvm-svn: 134403
diff --git a/clang/lib/Sema/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
index 951fbfa..0ecd814 100644
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -3228,7 +3228,8 @@
 
  public:
   explicit NamespaceSpecifierSet(ASTContext &Context, DeclContext *CurContext)
-      : Context(Context), CurContextChain(BuildContextChain(CurContext)) {}
+      : Context(Context), CurContextChain(BuildContextChain(CurContext)),
+        isSorted(true) {}
 
   /// \brief Add the namespace to the set, computing the corresponding
   /// NestedNameSpecifier and its distance in the process.