[proof-of-concept] SW thread independent of the main thread

content/browser/service_worker/service_worker_process_manager.cc

Index: content/browser/service_worker/service_worker_process_manager.cc
diff --git a/content/browser/service_worker/service_worker_process_manager.cc b/content/browser/service_worker/service_worker_process_manager.cc
index b6cdeb556c777b08f0af06dd85c18c2e1437777a..c97252a4989802550e9c40211c42a909bc283950 100644
--- a/content/browser/service_worker/service_worker_process_manager.cc
+++ b/content/browser/service_worker/service_worker_process_manager.cc
@@ -301,6 +301,20 @@ std::vector<int> ServiceWorkerProcessManager::SortProcessesForPattern(
   return result;
 }
 
+void ServiceWorkerProcessManager::FindAvailableProcessAndCallbackOnUI(
+    const GURL& pattern,
+    const base::Callback<void(int)> callback) {
+  if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
+    BrowserThread::PostTask(
+        BrowserThread::UI, FROM_HERE,
+        base::Bind(
+            &ServiceWorkerProcessManager::FindAvailableProcessAndCallbackOnUI,
+            weak_this_, pattern, callback));
+    return;
+  }
+  callback.Run(FindAvailableProcess(pattern));
+}
+
 int ServiceWorkerProcessManager::FindAvailableProcess(const GURL& pattern) {
   RenderProcessHost* backgrounded_candidate = nullptr;