hidl-gen: expose the actually-used FQNames an AST depends on

b/31015466
b/31045569

Change-Id: I0e8c27971fddee8a18e4209e7a8dff157fb71e8b
Signed-off-by: Iliyan Malchev <malchev@google.com>
diff --git a/AST.h b/AST.h
index 6af5604..cd13ac9 100644
--- a/AST.h
+++ b/AST.h
@@ -85,6 +85,13 @@
 
     bool isJavaCompatible() const;
 
+    // Return the set of FQNames for those interfaces and types that are
+    // actually referenced in the AST, not merely imported.
+
+    const std::set<FQName>& getImportedNames() const {
+        return mImportedNames;
+    }
+
 private:
     Coordinator *mCoordinator;
     std::string mPath;