Use non-default TaskRunner on CookieStore on ServiceWorkers

CookieStore on workers uses the default task runner to handle the async
IPC completion, which is deprecated.

This CL updates the IPC endpoint set up to use per-frame task runner
for finer priority control.

Bug: 961186
Change-Id: I45db9728d1315b31d0b570578bff34fe6be9cdd1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1626923
Commit-Queue: Victor Costan <pwnall@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663817}

third_party/blink/renderer/modules/cookie_store/service_worker_global_scope_cookie_store.cc

@@ -20,10 +20,14 @@ CookieStore* GlobalCookieStoreImpl<WorkerGlobalScope>::BuildCookieStore(
     ExecutionContext* execution_context,
     service_manager::InterfaceProvider* interface_provider) {
   network::mojom::blink::RestrictedCookieManagerPtr cookie_manager_ptr;
-  interface_provider->GetInterface(mojo::MakeRequest(&cookie_manager_ptr));
+  interface_provider->GetInterface(mojo::MakeRequest(
+      &cookie_manager_ptr,
+      execution_context->GetTaskRunner(TaskType::kMiscPlatformAPI)));
 
   blink::mojom::blink::CookieStorePtr cookie_store_ptr;
-  interface_provider->GetInterface(mojo::MakeRequest(&cookie_store_ptr));
+  interface_provider->GetInterface(mojo::MakeRequest(
+      &cookie_store_ptr,
+      execution_context->GetTaskRunner(TaskType::kMiscPlatformAPI)));
 
   return MakeGarbageCollected<CookieStore>(execution_context,
                                            std::move(cookie_manager_ptr),