fix(net): Allow preventDefault() on retry event (#8058)

Fixes #8041

Author: avelad

lib/net/networking_engine.js

@@ -667,8 +667,16 @@ shaka.net.NetworkingEngine = class extends shaka.util.FakeEventTarget {
         if (error.severity == shaka.util.Error.Severity.RECOVERABLE) {
           const data = (new Map()).set('error', error);
           const event = new shaka.util.FakeEvent('retry', data);
+          // A user can call preventDefault() on a cancelable event.
+          event.cancelable = true;
           this.dispatchEvent(event);
 
+          if (event.defaultPrevented) {
+            // If the caller uses preventDefault() on the 'retry' event, don't
+            // retry any more.
+            throw error;
+          }
+
           // Move to the next URI.
           index = (index + 1) % request.uris.length;
           return this.send_(

test/net/networking_engine_unit.js

@@ -63,6 +63,7 @@ describe('NetworkingEngine', /** @suppress {accessControls} */ () => {
   afterEach(() => {
     shaka.net.NetworkingEngine.unregisterScheme('resolve');
     shaka.net.NetworkingEngine.unregisterScheme('reject');
+    networkingEngine.destroy();
   });
 
   afterAll(() => {
@@ -142,6 +143,31 @@ describe('NetworkingEngine', /** @suppress {accessControls} */ () => {
       expect(rejectScheme).toHaveBeenCalledTimes(3);
     });
 
+    it('allow abort retry', async () => {
+      const request = createRequest('reject://foo', {
+        maxAttempts: 2,
+        baseDelay: 0,
+        backoffFactor: 0,
+        fuzzFactor: 0,
+        timeout: 0,
+        stallTimeout: 0,
+        connectionTimeout: 0,
+      });
+      rejectScheme.and.callFake(() => {
+        if (rejectScheme.calls.count() == 1) {
+          return shaka.util.AbortableOperation.failed(error);
+        } else {
+          return shaka.util.AbortableOperation.completed(createResponse());
+        }
+      });
+      networkingEngine.addEventListener('retry', (event) => {
+        event.preventDefault();
+      });
+      await expectAsync(networkingEngine.request(requestType, request).promise)
+          .toBeRejected();
+      expect(rejectScheme).toHaveBeenCalledTimes(1);
+    });
+
     describe('backoff', () => {
       const baseDelay = 200;
       const realRandom = Math.random;