Interop with EmberObject.extend on < 3.1

tests/integration/components/modifier-manager-test.js

@@ -2,6 +2,7 @@ import { module, test } from 'qunit';
 import { setupRenderingTest } from 'ember-qunit';
 import { render } from '@ember/test-helpers';
 import hbs from 'htmlbars-inline-precompile';
+import EmberObject from '@ember/object';
 import { assign } from '@ember/polyfills';
 import { capabilities, setModifierManager } from '@ember/modifier';
 
@@ -74,6 +75,55 @@ module('Integration | Component | modifier-manager', function(hooks) {
 
       await render(hbs`<div {{my-modifier}}></div>`);
     });
+
+
+    test('it can find the manager set on a native super-class', async function(assert) {
+      assert.expect(1);
+
+      class BaseModifier {}
+      class MyModifier extends BaseModifier {}
+
+      this.owner.register('modifier:my-modifier', MyModifier);
+
+      setModifierManager(
+        () => ({
+          capabilities: capabilities('3.13'),
+          createModifier(factory) {
+            assert.equal(factory.class, MyModifier, 'the factory class is Modifier');
+          },
+          installModifier() {},
+          updateModifier() {},
+          destroyModifier() {},
+        }),
+        BaseModifier
+      );
+
+      await render(hbs`<div {{my-modifier}}></div>`);
+    });
+
+    test('it can find the manager set on a EmberObject super-class', async function(assert) {
+      assert.expect(1);
+
+      const BaseModifier = EmberObject.extend({});
+      const MyModifier = BaseModifier.extend({});
+
+      this.owner.register('modifier:my-modifier', MyModifier);
+
+      setModifierManager(
+        () => ({
+          capabilities: capabilities('3.13'),
+          createModifier(factory) {
+            assert.equal(factory.class, MyModifier, 'the factory class is Modifier');
+          },
+          installModifier() {},
+          updateModifier() {},
+          destroyModifier() {},
+        }),
+        BaseModifier
+      );
+
+      await render(hbs`<div {{my-modifier}}></div>`);
+    });
   });
 
   module('installModifier', function(hooks) {

vendor/ember-modifier-manager-polyfill.js

@@ -22,7 +22,13 @@ import { deprecate } from '@ember/debug';
         return MODIFIER_MANAGERS.get(pointer);
       }
 
-      pointer = getPrototypeOf(pointer);
+      if (gte('3.1.0-beta.1')) {
+        pointer = getPrototypeOf(pointer);
+      } else if (Ember.Object.detect(pointer) && typeof pointer.superclass === 'function') {
+        pointer = pointer.superclass;
+      } else {
+        pointer = getPrototypeOf(pointer);
+      }
     }
 
     return;