ServiceWorker: Prevent worker script with incorrect MIME type to be registered.

content/browser/service_worker/service_worker_write_to_cache_job.cc

Index: content/browser/service_worker/service_worker_write_to_cache_job.cc
diff --git a/content/browser/service_worker/service_worker_write_to_cache_job.cc b/content/browser/service_worker/service_worker_write_to_cache_job.cc
index b3e6cadfcb424aea3600d289059509ac2562d4fd..bd60ba0236dade532ea847d61de7f09171973470 100644
--- a/content/browser/service_worker/service_worker_write_to_cache_job.cc
+++ b/content/browser/service_worker/service_worker_write_to_cache_job.cc
@@ -301,6 +301,18 @@ void ServiceWorkerWriteToCacheJob::OnResponseStarted(
     // response to our consumer, just don't cache it?
     return;
   }
+  // To prevent most user-uploaded content from being used as a serviceworker.
+  if (version_->script_url() == url_) {
+    std::string mime_type;
+    request->GetMimeType(&mime_type);
+    if (mime_type != "application/x-javascript" &&
+        mime_type != "text/javascript" &&
+        mime_type != "application/javascript") {
+      AsyncNotifyDoneHelper(net::URLRequestStatus(
+          net::URLRequestStatus::FAILED, net::ERR_FAILED));
+      return;
+    }
+  }
   WriteHeadersToCache();
 }