Extend hidl-gen to support generate vts file.

b/30762234

TODO: add regression test.

Change-Id: I1c31fd9a85805cd450ea03cc0ccc750a756d1009
diff --git a/AST.h b/AST.h
index 65dd016..da8f655 100644
--- a/AST.h
+++ b/AST.h
@@ -58,6 +58,9 @@
 
     void getImportedPackages(std::set<FQName> *importSet) const;
 
+    status_t generateVts(const std::string &outputPath) const;
+
+
 private:
     Coordinator *mCoordinator;
     Vector<Scope *> mScopePath;
@@ -110,6 +113,7 @@
 
     status_t emitTypeDeclarations(Formatter &out) const;
     status_t emitJavaTypeDeclarations(Formatter &out) const;
+    status_t emitVtsTypeDeclarations(Formatter &out, Vector<Type*> types) const;
 
     DISALLOW_COPY_AND_ASSIGN(AST);
 };