Stop dropping service worker scripts from MemoryCache

This was a hack to ensure service worker script requests go through
the browser process. This hack is no longer needed because script
requests happen on the worker thread and requests happened outside
the main thread are never put into MemoryCache.

Bug: 990659
Change-Id: I9450309e95a3116f0d03b5beb22a2e58ed343a61
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1735148Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Commit-Queue: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683895}

third_party/blink/renderer/modules/service_worker/service_worker_global_scope.cc

@@ -766,11 +766,6 @@ void ServiceWorkerGlobalScope::importScripts(
                             : stringOrUrl.GetAsTrustedScriptURL()->toString();
 
     KURL completed_url = CompleteURL(string_url);
-    // Bust the MemoryCache to ensure script requests reach the browser-side
-    // and get added to and retrieved from the ServiceWorker's script cache.
-    // FIXME: Revisit in light of the solution to crbug/388375.
-    RemoveURLFromMemoryCache(completed_url);
-
     if (installed_scripts_manager &&
         !installed_scripts_manager->IsScriptInstalled(completed_url)) {
       DCHECK(installed_scripts_manager->IsScriptInstalled(Url()));