Auto merge of #3045 - rust-lang:search-task-restartable, r=Turbo87

Keep only latest search API request

We are currently using the `drop` modifier for the data task, which means that subsequent requests are ignored while the first request is in flight.
Changing the modifier to `restartable` will take the data task drop all but the latest request. This should help with showing the correct search results when paginating and using the browser's back button.

Partially addresses #3041.

Author: bors

app/controllers/search.js

@@ -59,6 +59,6 @@ export default class SearchController extends Controller {
     }
 
     return yield this.store.query('crate', { all_keywords, page, per_page, q, sort });
-  }).drop())
+  }).restartable())
   dataTask;
 }