Fix blink::ResourceLoader finalization

This causes blink::ResourceLoader::Dispose() to close the object's
blink.mojom.ProgressClient binding, preventing incoming IPCs from
being dispatched to the finalized object in the interim between
finalization and actual destruction.

Bug: 867370
Change-Id: I9a14c51cb5d75e11b211006d094d73beafab8922
Reviewed-on: https://chromium-review.googlesource.com/1168289Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Ken Rockot <rockot@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581779}

third_party/blink/renderer/platform/loader/fetch/resource_loader.cc

@@ -823,6 +823,7 @@ void ResourceLoader::RequestSynchronously(const ResourceRequest& request) {
 
 void ResourceLoader::Dispose() {
   loader_ = nullptr;
+  progress_binding_.Close();
 
   // Release() should be called to release |scheduler_client_id_| beforehand in
   // DidFinishLoading() or DidFail(), but when a timer to call Cancel() is