Set up content in-process main threads via factory

content/browser/utility_process_host_impl.cc

Index: content/browser/utility_process_host_impl.cc
diff --git a/content/browser/utility_process_host_impl.cc b/content/browser/utility_process_host_impl.cc
index 2e562188d24d22199fca01170defd4762418b8c2..41f531a5e63143d0a75e344a44ece150d9cd3b3d 100644
--- a/content/browser/utility_process_host_impl.cc
+++ b/content/browser/utility_process_host_impl.cc
@@ -53,53 +53,8 @@ private:
 };
 #endif
 
-// We want to ensure there's only one utility thread running at a time, as there
-// are many globals used in the utility process.
-static base::LazyInstance<base::Lock> g_one_utility_thread_lock;
 
-// Single process not supported in multiple dll mode currently.
-#if !defined(CHROME_MULTIPLE_DLL)
-class UtilityMainThread : public base::Thread {
- public:
-  UtilityMainThread(const std::string& channel_id)
-      : Thread("Chrome_InProcUtilityThread"),
-        channel_id_(channel_id) {
-  }
-
-  virtual ~UtilityMainThread() {
-    Stop();
-  }
-
- private:
-  // base::Thread implementation:
-  virtual void Init() OVERRIDE {
-    // We need to return right away or else the main thread that started us will
-    // hang.
-    base::MessageLoop::current()->PostTask(
-        FROM_HERE,
-        base::Bind(&UtilityMainThread::InitInternal, base::Unretained(this)));
-  }
-
-  virtual void CleanUp() OVERRIDE {
-    child_process_.reset();
-
-    // See comment in RendererMainThread.
-    SetThreadWasQuitProperly(true);
-    g_one_utility_thread_lock.Get().Release();
-  }
-
-  void InitInternal() {
-    g_one_utility_thread_lock.Get().Acquire();
-    child_process_.reset(new ChildProcess());
-    child_process_->set_main_thread(new UtilityThreadImpl(channel_id_));
-  }
-
-  std::string channel_id_;
-  scoped_ptr<ChildProcess> child_process_;
-
-  DISALLOW_COPY_AND_ASSIGN(UtilityMainThread);
-};
-#endif  // !CHROME_MULTIPLE_DLL
+UtilityMainThreadFactoryFunction g_utility_main_thread_factory = NULL;
 
 UtilityProcessHost* UtilityProcessHost::Create(
     UtilityProcessHostClient* client,
@@ -107,6 +62,11 @@ UtilityProcessHost* UtilityProcessHost::Create(
   return new UtilityProcessHostImpl(client, client_task_runner);
 }
 
+void UtilityProcessHost::RegisterUtilityMainThreadFactory(
+    UtilityMainThreadFactoryFunction create) {
+  g_utility_main_thread_factory = create;
+}
+
 UtilityProcessHostImpl::UtilityProcessHostImpl(
     UtilityProcessHostClient* client,
     base::SequencedTaskRunner* client_task_runner)
@@ -196,15 +156,13 @@ bool UtilityProcessHostImpl::StartProcess() {
     return false;
 
   // Single process not supported in multiple dll mode currently.
-#if !defined(CHROME_MULTIPLE_DLL)
-  if (RenderProcessHost::run_renderer_in_process()) {
+  if (RenderProcessHost::run_renderer_in_process() &&
+      g_utility_main_thread_factory) {
     // See comment in RenderProcessHostImpl::Init() for the background on why we
     // support single process mode this way.
-    in_process_thread_.reset(new UtilityMainThread(channel_id));
+    in_process_thread_.reset(g_utility_main_thread_factory(channel_id));
     in_process_thread_->Start();
-  } else
-#endif  // !CHROME_MULTIPLE_DLL
-  {
+  } else {
     const CommandLine& browser_command_line = *CommandLine::ForCurrentProcess();
     int child_flags = child_flags_;