[Extensions] Remove inline TaskObserver constructor and destructor.

Chrome style forbids complex inline constructors and destructors.

Bug: 966655
Change-Id: I77c38d7af6a0f4d1193569eaff18e9ee8700aa2b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1633409Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: David Bertoni <dbertoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664528}

extensions/browser/service_worker_task_queue.cc

@@ -53,6 +53,10 @@ ServiceWorkerTaskQueue::ServiceWorkerTaskQueue(BrowserContext* browser_context)
 
 ServiceWorkerTaskQueue::~ServiceWorkerTaskQueue() {}
 
+ServiceWorkerTaskQueue::TestObserver::TestObserver() {}
+
+ServiceWorkerTaskQueue::TestObserver::~TestObserver() {}
+
 // static
 ServiceWorkerTaskQueue* ServiceWorkerTaskQueue::Get(BrowserContext* context) {
   return ServiceWorkerTaskQueueFactory::GetForBrowserContext(context);

extensions/browser/service_worker_task_queue.h

@@ -75,8 +75,8 @@ class ServiceWorkerTaskQueue : public KeyedService,
 
   class TestObserver {
    public:
-    TestObserver() = default;
-    virtual ~TestObserver() = default;
+    TestObserver();
+    virtual ~TestObserver();
 
     // Called when an extension with id |extension_id| is going to be activated.
     // |will_register_service_worker| is true if a Service Worker will be