Move ProxyConfigService construction onto the IO thread.

net/proxy/proxy_config_service_linux.h

Index: net/proxy/proxy_config_service_linux.h
diff --git a/net/proxy/proxy_config_service_linux.h b/net/proxy/proxy_config_service_linux.h
index 8d46d998c6396b6599a83779dc29f4b3d3914d4d..58928b58bbf0e3b47ef0b9110d6e998355dd60c3 100644
--- a/net/proxy/proxy_config_service_linux.h
+++ b/net/proxy/proxy_config_service_linux.h
@@ -139,10 +139,9 @@ class NET_EXPORT_PRIVATE ProxyConfigServiceLinux : public ProxyConfigService {
     DISALLOW_COPY_AND_ASSIGN(SettingGetter);
   };
 
-  // ProxyConfigServiceLinux is created on the UI thread, and
-  // SetUpAndFetchInitialConfig() is immediately called to synchronously
-  // fetch the original configuration and set up change notifications on
-  // the UI thread.
+  // ProxyConfigServiceLinux is created on the IO thread, and begins
+  // asynchronously on the UI thread fetching the original configuration
+  // and setting up change notifications.
   //
   // Past that point, it is accessed periodically through the
   // ProxyConfigService interface (GetLatestProxyConfig, AddObserver,
@@ -155,13 +154,15 @@ class NET_EXPORT_PRIVATE ProxyConfigServiceLinux : public ProxyConfigService {
   // Delegate::SetNewProxyConfig(). We then notify observers on the IO
   // thread of the configuration change.
   //
-  // ProxyConfigServiceLinux is deleted from the IO thread.
+  // ProxyConfigServiceLinux is deleted from the IO thread but may require
+  // prior shutdown performed on other threads via StartTearDown().
+  // This prior shutdown safely stops change notifications.
   //
   // The substance of the ProxyConfigServiceLinux implementation is
-  // wrapped in the Delegate ref counted class. On deleting the
-  // ProxyConfigServiceLinux, Delegate::OnDestroy() is posted to either
-  // the UI thread (gconf/gsettings) or the file thread (KDE) where change
-  // notifications will be safely stopped before releasing Delegate.
+  // wrapped in the Delegate ref counted class. Destruction of the Delegate
+  // is commenced by StartTearDown() which calls Delegate::OnDestroy() on
+  // the UI thread (gconf/gsettings) or posts it to the file thread (KDE) where
+  // change notifications will be safely stopped before releasing Delegate.
 
   class Delegate : public base::RefCountedThreadSafe<Delegate> {
    public:
@@ -172,14 +173,8 @@ class NET_EXPORT_PRIVATE ProxyConfigServiceLinux : public ProxyConfigService {
     // to use, and takes ownership of them. Used for testing.
     Delegate(base::Environment* env_var_getter, SettingGetter* setting_getter);
 
-    // Synchronously obtains the proxy configuration. If gconf,
-    // gsettings, or kioslaverc are used, also enables notifications for
-    // setting changes. gconf/gsettings must only be accessed from the
-    // thread running the default glib main loop, and so this method
-    // must be called from the UI thread. The message loop for the IO
-    // thread is specified so that notifications can post tasks to it
-    // (and for assertions). The message loop for the file thread is
-    // used to read any files needed to determine proxy settings.
+    // Posts SetUpAndFetchInitialConfigOnUIThread() to UI thread.  Called
+    // from the IO thread.
     void SetUpAndFetchInitialConfig(
         base::SingleThreadTaskRunner* glib_thread_task_runner,
         base::SingleThreadTaskRunner* io_thread_task_runner,
@@ -199,7 +194,8 @@ class NET_EXPORT_PRIVATE ProxyConfigServiceLinux : public ProxyConfigService {
         ProxyConfig* config);
 
     // Posts a call to OnDestroy() to the UI or FILE thread, depending on the
-    // setting getter in use. Called from ProxyConfigServiceLinux's destructor.
+    // setting getter in use. Called from
+    // ProxyConfigServiceLinux::StartTearDown().
     void PostDestroyTask();
     // Safely stops change notifications. Posted to either the UI or FILE
     // thread, depending on the setting getter in use.
@@ -210,6 +206,14 @@ class NET_EXPORT_PRIVATE ProxyConfigServiceLinux : public ProxyConfigService {
 
     ~Delegate();
 
+    // Synchronously obtains the proxy configuration. If gconf,
+    // gsettings, or kioslaverc are used, also enables notifications for
+    // setting changes. gconf/gsettings must only be accessed from the
+    // thread running the default glib main loop, and so this method
+    // must be called from the UI thread.

[digit1, 2012/10/19 10:32:46]

On the other hand, this comment is probably perfectly fine and informative :)

+    void SetUpAndFetchInitialConfigOnUIThread(
+        MessageLoopForIO* file_loop);
+
     // Obtains an environment variable's value. Parses a proxy server
     // specification from it and puts it in result. Returns true if the
     // requested variable is defined and the value valid.
@@ -241,9 +245,11 @@ class NET_EXPORT_PRIVATE ProxyConfigServiceLinux : public ProxyConfigService {
     scoped_ptr<base::Environment> env_var_getter_;
     scoped_ptr<SettingGetter> setting_getter_;
 
+    // Has initialization completed and it's safe to read cached_config_.
+    bool finished_initialization_;
+
     // Cached proxy configuration, to be returned by
-    // GetLatestProxyConfig. Initially populated from the UI thread, but
-    // afterwards only accessed from the IO thread.
+    // GetLatestProxyConfig. Only accessed from the IO thread.
     ProxyConfig cached_config_;
 
     // A copy kept on the UI thread of the last seen proxy config, so as
@@ -272,7 +278,10 @@ class NET_EXPORT_PRIVATE ProxyConfigServiceLinux : public ProxyConfigService {
   // Thin wrapper shell around Delegate.
 
   // Usual constructor
-  ProxyConfigServiceLinux();
+  ProxyConfigServiceLinux(
+      base::SingleThreadTaskRunner* glib_thread_task_runner,
+      base::SingleThreadTaskRunner* io_thread_task_runner,
+      MessageLoopForIO* file_loop);
   // For testing: take alternate setting and env var getter implementations.
   explicit ProxyConfigServiceLinux(base::Environment* env_var_getter);
   ProxyConfigServiceLinux(base::Environment* env_var_getter,
@@ -280,6 +289,7 @@ class NET_EXPORT_PRIVATE ProxyConfigServiceLinux : public ProxyConfigService {
 
   virtual ~ProxyConfigServiceLinux();
 
+  // This is only public for testing.
   void SetupAndFetchInitialConfig(
       base::SingleThreadTaskRunner* glib_thread_task_runner,
       base::SingleThreadTaskRunner* io_thread_task_runner,
@@ -297,7 +307,8 @@ class NET_EXPORT_PRIVATE ProxyConfigServiceLinux : public ProxyConfigService {
   virtual void RemoveObserver(Observer* observer) OVERRIDE;
   virtual ProxyConfigService::ConfigAvailability GetLatestProxyConfig(
       ProxyConfig* config) OVERRIDE;
-
+  // Called from Glib thread.
+  virtual void StartTearDown() OVERRIDE;
  private:
   scoped_refptr<Delegate> delegate_;