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

content/browser/service_worker/service_worker_process_manager.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/service_worker/service_worker_process_manager.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <utility>
@@ skipping 283 matching lines @@
   std::vector<std::pair<int, int> > counted(
       it->second.begin(), it->second.end());
   std::sort(counted.begin(), counted.end(), SecondGreater());
 
   std::vector<int> result(counted.size());
   for (size_t i = 0; i < counted.size(); ++i)
     result[i] = counted[i].first;
   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;
 
   // Try to find an available foreground process.
   std::vector<int> sorted_candidates = SortProcessesForPattern(pattern);
   for (int process_id : sorted_candidates) {
     RenderProcessHost* rph = RenderProcessHost::FromID(process_id);
     if (!rph || rph->FastShutdownStarted())
       continue;
 
@@ skipping 19 matching lines @@
 namespace std {
 // Destroying ServiceWorkerProcessManagers only on the UI thread allows the
 // member WeakPtr to safely guard the object's lifetime when used on that
 // thread.
 void default_delete<content::ServiceWorkerProcessManager>::operator()(
     content::ServiceWorkerProcessManager* ptr) const {
   content::BrowserThread::DeleteSoon(
       content::BrowserThread::UI, FROM_HERE, ptr);
 }
 }  // namespace std