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..c68890f792a8404dd35953e56bcad710f3831432 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 +46,26 @@ self.addEventListener('message', function(workerEvent) {
         }).catch(makeErrorHandler(event.data.command));
         break;
 
+      case 'checkInterfaces':
+        var success = false;
+        var message = "";
+        try {
+          if ('BudgetService' in self &&
+              WorkerNavigator.prototype.hasOwnProperty('budget') &&
+              BudgetService.prototype.hasOwnProperty('getCost') &&
+              BudgetService.prototype.hasOwnProperty('getBudget') &&
+              BudgetService.prototype.hasOwnProperty('reserve')
+             )
+            success = true;
+        } catch(err) {
+          message = err.message;
+        }

[Peter Beverloo, 2016/12/12 14:28:43]

What exception do you expect to be thrown here? I don't think there is any.

The following would be much nicer:

const success = 'BudgetService' in self &&
                BudgetService.prototype.hasOwnProperty('getCost') &&
                BudgetService.prototype.hasOwnProperty('getBudget') &&
                BudgetService.prototype.hasOwnProperty('reserve') &&
                WorkerNavigator.prototype.hasOwnProperty('budget');

port.postMessage({ .. });

[harkness, 2016/12/12 16:00:34]

Updated the code to remove the if statement, but left the try in. 

I used that a lot when I was testing because without that, the test just times
out without giving any information if there is an exception. While I was
testing, the exception was because I was using Navigator or navigator instead of
WorkerNavigator, but it could also happen if you accidentally deleted a
character in any of the names, and the timeout is very difficult to debug but
with the exception message, it's quick to track down.

+        port.postMessage({
+          command: event.data.command,
+          success: success,
+          message: message});
+        break;
+
       default:
         port.postMessage({
           command: 'error',