service worker: Use fake network provider in WebEmbeddedWorkerImplTest.

WebEmbeddedWorkerImplTest was using a null ServiceWorkerNetworkProvider.
This CL adds a fake provider which implements CreateURLLoader() to
return non-null, which matches the ServiceWorkerServicification
behavior.  This removes callsites to
Platform::CreateDefaultURLLoaderFactory() via
WorkerShadowPage::CreateURLLoaderFactory(), which is being removed at
bug 891872.

Bug: 891872
Change-Id: I8592131fea83429b39b9744727a4bdd493734be0
Reviewed-on: https://chromium-review.googlesource.com/c/1361754
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613836}
1 file changed