[libclang] When parsing with CXTranslationUnit_ForSerialization, make sure to install the ASTWriter that we create as an ASTMutationListener.

Fixes rdar://13833268

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@181575 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/ASTUnit.cpp b/lib/Frontend/ASTUnit.cpp
index f05d722..7850dc6 100644
--- a/lib/Frontend/ASTUnit.cpp
+++ b/lib/Frontend/ASTUnit.cpp
@@ -638,6 +638,12 @@
     StoredDiags.push_back(StoredDiagnostic(Level, Info));
 }
 
+ASTMutationListener *ASTUnit::getASTMutationListener() {
+  if (WriterData)
+    return &WriterData->Writer;
+  return 0;
+}
+
 ASTDeserializationListener *ASTUnit::getDeserializationListener() {
   if (WriterData)
     return &WriterData->Writer;
@@ -929,6 +935,10 @@
       handleTopLevelDecl(*it);
   }
 
+  virtual ASTMutationListener *GetASTMutationListener() {
+    return Unit.getASTMutationListener();
+  }
+
   virtual ASTDeserializationListener *GetASTDeserializationListener() {
     return Unit.getDeserializationListener();
   }