Recommit 213307: unique_ptr-ify ownership of ASTConsumers (reverted in r213325)

After post-commit review and community discussion, this seems like a
reasonable direction to continue, making ownership semantics explicit in
the source using the type system.

llvm-svn: 215323
diff --git a/clang/unittests/Frontend/FrontendActionTest.cpp b/clang/unittests/Frontend/FrontendActionTest.cpp
index 44843ee..cb9cc52 100644
--- a/clang/unittests/Frontend/FrontendActionTest.cpp
+++ b/clang/unittests/Frontend/FrontendActionTest.cpp
@@ -38,9 +38,9 @@
     return ASTFrontendAction::BeginSourceFileAction(ci, filename);
   }
 
-  virtual ASTConsumer *CreateASTConsumer(CompilerInstance &CI,
-                                         StringRef InFile) {
-    return new Visitor(decl_names);
+  virtual std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &CI,
+                                                         StringRef InFile) {
+    return llvm::make_unique<Visitor>(decl_names);
   }
 
 private: