Enhanced hidl-gen support for generating vts files.

*Support callflow from mehtod annotations.
*Support inheritance for interfaces and types.
*Support Array and Union type.

b/30762234

Change-Id: I059b780d6362a557bb9cfd70d6c5ec0e73916ce3
diff --git a/VectorType.h b/VectorType.h
index c4dbd63..9f76314 100644
--- a/VectorType.h
+++ b/VectorType.h
@@ -37,6 +37,7 @@
     bool resultNeedsDeref() const override;
 
     status_t emitVtsTypeDeclarations(Formatter &out) const override;
+    status_t emitVtsAttributeType(Formatter &out) const override;
 
     bool isJavaCompatible() const override;