fix(service-worker): PushEvent.data has to be decoded (#19764)

PushEvent.data is not the data object itself, but an instance representing
the data in wire format, with methods to synchronously decode it to JSON,
ArrayBuffer, etc. NGSW assumes all push data is in JSON format.

PR Close #19764

packages/service-worker/worker/src/driver.ts

@@ -224,7 +224,7 @@ export class Driver implements Debuggable, UpdateSource {
     }
 
     // Handle the push and keep the SW alive until it's handled.
-    msg.waitUntil(this.handlePush(msg.data));
+    msg.waitUntil(this.handlePush(msg.data.json()));
   }
 
   private async handleMessage(msg: MsgAny&{action: string}, from: Client): Promise<void> {

packages/service-worker/worker/testing/scope.ts

@@ -324,7 +324,10 @@ class MockMessageEvent extends MockExtendableEvent {
 }
 
 class MockPushEvent extends MockExtendableEvent {
-  constructor(readonly data: Object) { super(); }
+  constructor(private _data: Object) { super(); }
+  data = {
+    json: () => this._data,
+  };
 }
 
 class MockInstallEvent extends MockExtendableEvent {}