Remove DCHECK from GetWindowClientInfoOnUI

As discussed in the bug, the condition under DCHECK is legitimate, and
the existing code does no harm in this case.

Bug: 923806
Change-Id: I5c46ac94174ba91184d6a5dad46702899abef95e
Reviewed-on: https://chromium-review.googlesource.com/c/1431613
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625438}

content/browser/service_worker/service_worker_client_utils.cc

@@ -128,8 +128,6 @@ blink::mojom::ServiceWorkerClientInfoPtr GetWindowClientInfoOnUI(
   // for a frame that is actually being navigated and isn't exactly what we are
   // expecting.
   PageVisibilityState visibility = render_frame_host->GetVisibilityState();
-  // Service workers do no prerender, this would be an invalid visibility state.
-  DCHECK_NE(visibility, PageVisibilityState::kPrerender);
   bool page_hidden = visibility != PageVisibilityState::kVisible;
   return blink::mojom::ServiceWorkerClientInfo::New(
       render_frame_host->GetLastCommittedURL(),