Mojo C++ Bindings: Extract AssociatedGroupController from MultiplexRouter

mojo/public/cpp/bindings/BUILD.gn

Index: mojo/public/cpp/bindings/BUILD.gn
diff --git a/mojo/public/cpp/bindings/BUILD.gn b/mojo/public/cpp/bindings/BUILD.gn
index 6594d7683667b813fa74e27ebfcdca9aa657721a..8ff7905578ee8d4b35703eddaa320fd2dfc13bb2 100644
--- a/mojo/public/cpp/bindings/BUILD.gn
+++ b/mojo/public/cpp/bindings/BUILD.gn
@@ -11,12 +11,16 @@ source_set("bindings") {
     "array_traits_stl.h",
     "associated_binding.h",
     "associated_group.h",
+    "associated_group_controller.h",
     "associated_interface_ptr.h",
     "associated_interface_ptr_info.h",
     "associated_interface_request.h",
     "binding.h",
     "binding_set.h",
     "enum_traits.h",
+    "interface_endpoint_client.h",
+    "interface_endpoint_controller.h",
+    "interface_id.h",
     "interface_ptr.h",
     "interface_ptr_info.h",
     "interface_ptr_set.h",
@@ -25,6 +29,7 @@ source_set("bindings") {
     "lib/array_internal.h",
     "lib/array_serialization.h",
     "lib/associated_group.cc",
+    "lib/associated_group_controller.cc",
     "lib/associated_interface_ptr_state.h",
     "lib/binding_state.h",
     "lib/bindings_internal.h",
@@ -41,9 +46,6 @@ source_set("bindings") {
     "lib/fixed_buffer.h",
     "lib/handle_interface_serialization.h",
     "lib/interface_endpoint_client.cc",
-    "lib/interface_endpoint_client.h",
-    "lib/interface_endpoint_controller.h",
-    "lib/interface_id.h",
     "lib/interface_ptr_state.h",
     "lib/map_data_internal.h",
     "lib/map_serialization.h",