Have content/ create and destroy its own threads.

content/shell/shell_browser_main.cc

Index: content/shell/shell_browser_main.cc
diff --git a/content/shell/shell_browser_main.cc b/content/shell/shell_browser_main.cc
index a3364040b13f1cc98362197c3c5660296601b4d2..2a9bd95bd9d44a5403490303ab2c7e92900d38f5 100644
--- a/content/shell/shell_browser_main.cc
+++ b/content/shell/shell_browser_main.cc
@@ -29,41 +29,9 @@ ShellBrowserMainParts::ShellBrowserMainParts(
 }
 
 ShellBrowserMainParts::~ShellBrowserMainParts() {
-  base::ThreadRestrictions::SetIOAllowed(true);
-    io_thread()->message_loop()->PostTask(
-        FROM_HERE,
-        NewRunnableFunction(&base::ThreadRestrictions::SetIOAllowed, true));
-
-  browser_context_.reset();
-
-  resource_dispatcher_host_->download_file_manager()->Shutdown();
-  resource_dispatcher_host_->save_file_manager()->Shutdown();
-  resource_dispatcher_host_->Shutdown();
-  io_thread_.reset();
-  cache_thread_.reset();
-  process_launcher_thread_.reset();
-  file_thread_.reset();
-  resource_dispatcher_host_.reset();  // Kills WebKit thread.
-  db_thread_.reset();
 }
 
-void ShellBrowserMainParts::PreMainMessageLoopRun() {
-  db_thread_.reset(new BrowserProcessSubThread(BrowserThread::DB));
-  db_thread_->Start();
-  file_thread_.reset(new BrowserProcessSubThread(BrowserThread::FILE));
-  file_thread_->Start();
-  process_launcher_thread_.reset(
-      new BrowserProcessSubThread(BrowserThread::PROCESS_LAUNCHER));
-  process_launcher_thread_->Start();
-
-  base::Thread::Options options;
-  options.message_loop_type = MessageLoop::TYPE_IO;
-
-  cache_thread_.reset(new BrowserProcessSubThread(BrowserThread::CACHE));
-  cache_thread_->StartWithOptions(options);
-  io_thread_.reset(new BrowserProcessSubThread(BrowserThread::IO));
-  io_thread_->StartWithOptions(options);
-
+content::IOThreadDelegate* ShellBrowserMainParts::PreMainMessageLoopRun() {
   browser_context_.reset(new ShellBrowserContext(this));
 
   Shell::PlatformInitialize();
@@ -74,7 +42,23 @@ void ShellBrowserMainParts::PreMainMessageLoopRun() {
                          NULL,
                          MSG_ROUTING_NONE,
                          NULL);
+  return NULL;
+}
+
+void ShellBrowserMainParts::PostMainMessageLoopRun() {
+  browser_context_.reset();
 
+  resource_dispatcher_host_->download_file_manager()->Shutdown();
+  resource_dispatcher_host_->save_file_manager()->Shutdown();
+  resource_dispatcher_host_->Shutdown();
+}
+
+void ShellBrowserMainParts::PreStopThread(BrowserThread::ID id) {
+  if (id == BrowserThread::WEBKIT) {
+    // It remains the embedder's responsibility to kill the WebKit
+    // thread.  This happens when RDH is destroyed.
+    resource_dispatcher_host_.reset();
+  }
 }
 
 bool ShellBrowserMainParts::MainMessageLoopRun(int* result_code) {