fix(chip-list): stateChanges stream not being completed (#8636)

Fixes the `stateChanges` subject not being completed, potentially causing a memory leak if the subscribers forget to unsubscribe.

Author: crisbeto

src/lib/chips/chip-list.spec.ts

@@ -346,6 +346,15 @@ describe('MatChipList', () => {
       });
     });
 
+    it('should complete the stateChanges stream on destroy', () => {
+      const spy = jasmine.createSpy('stateChanges complete');
+      const subscription = chipListInstance.stateChanges.subscribe(undefined, undefined, spy);
+
+      fixture.destroy();
+      expect(spy).toHaveBeenCalled();
+      subscription.unsubscribe();
+    });
+
   });
 
   describe('selection logic', () => {

src/lib/chips/chip-list.ts

@@ -376,6 +376,7 @@ export class MatChipList extends _MatChipListMixinBase implements MatFormFieldCo
       this._changeSubscription.unsubscribe();
     }
     this._dropSubscriptions();
+    this.stateChanges.complete();
   }