Worker: Make DedicatedWorkerService::OnFinalResponseURLDetermined() pure-virtual

Bug: n/a
Change-Id: I402bca91778b5dc65066a8586d4771cc3e9b19ca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2409676Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Reviewed-by: Asami Doi <asamidoi@chromium.org>
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Cr-Commit-Position: refs/heads/master@{#806836}

content/public/browser/dedicated_worker_service.h

@@ -33,11 +33,9 @@ class CONTENT_EXPORT DedicatedWorkerService {
 
     // Called when the final response URL (the URL after redirects) was
     // determined when fetching the worker's script.
-    //
-    // TODO(pmonette): Implement this in derived classes and make it pure.
     virtual void OnFinalResponseURLDetermined(
         const blink::DedicatedWorkerToken& worker_token,
-        const GURL& url) {}
+        const GURL& url) = 0;
   };
 
   // Adds/removes an observer.