Added browser tests to test the BudgetAPI. Also added BudgetAPI to ExperimentalWebPlatformFeatures.

chrome/test/data/budget_service/service_worker.js

Index: chrome/test/data/budget_service/service_worker.js
diff --git a/chrome/test/data/budget_service/service_worker.js b/chrome/test/data/budget_service/service_worker.js
new file mode 100644
index 0000000000000000000000000000000000000000..4980c8efebc819f3c840d8ace375f354f91b09f7
--- /dev/null
+++ b/chrome/test/data/budget_service/service_worker.js
@@ -0,0 +1,52 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Accept messages from the test JavaScript to trigger worker based tests.
+self.addEventListener('message', function handler (event) {
+  if (event.data.command == 'workerGet') {
+    self.workerGetBudget();
+  } else if (event.data.command == 'workerReserve') {
+    self.workerReserve();

[Peter Beverloo, 2016/09/27 15:57:47]

nit: drop the |self| everywhere. That's the global, so it's bound to be
available.

[harkness, 2016/09/28 12:29:21]

Done.

+  } else {
+    sendMessageToClients('message', 'error - unknown message request');
+    return;
+  }
+});
+
+// Query for the budget and return the current total.
+function workerGetBudget() {

[Peter Beverloo, 2016/09/27 15:57:47]

Since we shipped async/await, you can use a much fancier way of writing this
function now:

async function workerGetBudget() {
  try {
    const budget = await navigator.budget.getBudget();
    sendMessageToClients(
        'message', 'ok - budget returned value of ' + budget[0].budgetAt);
  } catch (e) {
    sendMessageToClients('message', 'failed - unable to get budget values');
  }
}

(Also mixing up single and double quotes in the same function call is pushing it
a bit.)

[harkness, 2016/09/28 12:29:21]

Actually, when I tried to switch to async, the service worker parsing fails. I
went ahead and fixed the quotes though.

+  navigator.budget.getBudget().then(function(budget) {
+    sendMessageToClients('message',
+        "ok - budget returned value of " + budget[0].budgetAt);
+  }, function() {
+    sendMessageToClients('message', "failed - unable to get budget values");
+  });
+}
+
+// Request a reservation for a silent push.
+function workerReserve() {
+  navigator.budget.reserve('silent-push').then(function(reserved) {
+    if (reserved)
+      sendMessageToClients('message', "ok - reserved budget");
+    else
+      sendMessageToClients('message', "failed - not able to reserve budget");
+  }, function() {
+    sendMessageToClients('message',
+        "failed - error while trying to reserve budget");
+  });
+}
+
+function sendMessageToClients(type, data) {
+  var message = JSON.stringify({

[Peter Beverloo, 2016/09/27 15:57:47]

nit: use destructoring, don't use var.

const message = JSON.stringify({ type, data });

[harkness, 2016/09/28 12:29:21]

Done.

[Peter Beverloo, 2016/09/28 13:04:26]

This hasn't been done.

+    'type': type,
+    'data': data
+  });
+  clients.matchAll().then(function(clients) {
+    clients.forEach(function(client) {
+      client.postMessage(message);
+    });
+  }, function(error) {
+    console.log(error);
+  });

[Peter Beverloo, 2016/09/27 15:57:47]

If this were an async function, you could replace lines 45 - 51 with:

for (const client of await clients.matchAll())
  client.postMessage(message);

:)

[harkness, 2016/09/28 12:29:21]

Same issues as above.

+}