Expose the BudgetService interface to Workers.

third_party/WebKit/LayoutTests/http/tests/budget/resources/instrumentation-service-worker.js

Index: third_party/WebKit/LayoutTests/http/tests/budget/resources/instrumentation-service-worker.js
diff --git a/third_party/WebKit/LayoutTests/http/tests/budget/resources/instrumentation-service-worker.js b/third_party/WebKit/LayoutTests/http/tests/budget/resources/instrumentation-service-worker.js
index faafdc685c4428e47e44dfb41d3b86e2a2fb6836..c4491ec18e191abe9c78231046a2f40cf57669fc 100644
--- a/third_party/WebKit/LayoutTests/http/tests/budget/resources/instrumentation-service-worker.js
+++ b/third_party/WebKit/LayoutTests/http/tests/budget/resources/instrumentation-service-worker.js
@@ -46,6 +46,24 @@ self.addEventListener('message', function(workerEvent) {
         }).catch(makeErrorHandler(event.data.command));
         break;
 
+      case 'checkInterfaces':
+        let success = false;
+        let message = "";
+        try {
+          success = 'BudgetService' in self &&
+              WorkerNavigator.prototype.hasOwnProperty('budget') &&
+              BudgetService.prototype.hasOwnProperty('getCost') &&
+              BudgetService.prototype.hasOwnProperty('getBudget') &&
+              BudgetService.prototype.hasOwnProperty('reserve')
+        } catch(err) {
+          message = err.message;
+        }
+        port.postMessage({
+          command: event.data.command,
+          success: success,
+          message: message});
+        break;
+
       default:
         port.postMessage({
           command: 'error',