diff --git a/src/component_manager_impl.h b/src/component_manager_impl.h
index 4f15ecd..9778a93 100644
--- a/src/component_manager_impl.h
+++ b/src/component_manager_impl.h
@@ -147,6 +147,17 @@
   // tree. No sub-components are searched.
   std::string FindComponentWithTrait(const std::string& trait) const override;
 
+  // Support for legacy APIs. Setting command and state definitions.
+  // This translates into modifying a trait definition.
+  bool AddLegacyCommandDefinitions(const base::DictionaryValue& dict,
+                                   ErrorPtr* error) override;
+  bool AddLegacyStateDefinitions(const base::DictionaryValue& dict,
+                                 ErrorPtr* error) override;
+  // Returns device state for legacy APIs.
+  const base::DictionaryValue& GetLegacyState() const override;
+  // Returns command definitions for legacy APIs.
+  const base::DictionaryValue& GetLegacyCommandDefinitions() const override;
+
  private:
   // A helper method to find a JSON element of component at |path| to add new
   // sub-components to.
@@ -155,6 +166,12 @@
   base::DictionaryValue* FindMutableComponent(const std::string& path,
                                               ErrorPtr* error);
 
+  // Legacy API support: Helper function to support state/command definitions.
+  // Adds the given trait to at least one component.
+  // Searches for available components and if none of them already supports this
+  // trait, it adds it to the first available component.
+  void AddTraitToLegacyComponent(const std::string& trait);
+
   // Helper method to find a sub-component given a root node and a relative path
   // from the root to the target component.
   static const base::DictionaryValue* FindComponentAt(
@@ -178,6 +195,10 @@
   // Callback list for state change queue event sinks.
   base::CallbackList<void(UpdateID)> on_server_state_updated_;
 
+  // Legacy API support.
+  mutable base::DictionaryValue legacy_state_;  // Device state.
+  mutable base::DictionaryValue legacy_command_defs_;  // Command definitions.
+
   DISALLOW_COPY_AND_ASSIGN(ComponentManagerImpl);
 };