Pref service: add support for tracked prefs.

chrome/browser/prefs/chrome_pref_service_factory.cc

Index: chrome/browser/prefs/chrome_pref_service_factory.cc
diff --git a/chrome/browser/prefs/chrome_pref_service_factory.cc b/chrome/browser/prefs/chrome_pref_service_factory.cc
index 1e9b90229df9be9a8344347c2ff891c09d1c037e..4b3361d422c270db3a05d682f4dbe20fb1a0f9f0 100644
--- a/chrome/browser/prefs/chrome_pref_service_factory.cc
+++ b/chrome/browser/prefs/chrome_pref_service_factory.cc
@@ -58,6 +58,7 @@
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/browser_thread.h"
 #include "extensions/features/features.h"
+#include "mojo/public/cpp/bindings/strong_binding.h"
 #include "rlz/features/features.h"
 #include "services/preferences/public/cpp/tracked/configuration.h"
 #include "services/preferences/public/cpp/tracked/pref_names.h"
@@ -358,7 +359,7 @@ std::unique_ptr<ProfilePrefStoreManager> CreateProfilePrefStoreManager(
 #endif
   return base::MakeUnique<ProfilePrefStoreManager>(
       profile_path, GetTrackingConfiguration(), kTrackedPrefsReportingIDsCount,
-      seed, legacy_device_id, g_browser_process->local_state());
+      seed, legacy_device_id);
 }
 
 void PrepareFactory(sync_preferences::PrefServiceSyncableFactory* factory,
@@ -392,6 +393,28 @@ void PrepareFactory(sync_preferences::PrefServiceSyncableFactory* factory,
       ChromePrefModelAssociatorClient::GetInstance());
 }
 
+class ResetOnLoadObserverImpl : public prefs::mojom::ResetOnLoadObserver {
+ public:
+  explicit ResetOnLoadObserverImpl(const base::FilePath& profile_path)
+      : profile_path_(profile_path) {}
+
+  void OnResetOnLoad() override {
+    // A StartSyncFlare used to kick sync early in case of a reset event. This
+    // is done since sync may bring back the user's server value post-reset
+    // which could potentially cause a "settings flash" between the factory
+    // default and the re-instantiated server value. Starting sync ASAP
+    // minimizes the window before the server value is re-instantiated (this
+    // window can otherwise be as long as 10 seconds by default).
+    sync_start_util::GetFlareForSyncableService(profile_path_)
+        .Run(syncer::PREFERENCES);
+  }
+
+ private:
+  const base::FilePath profile_path_;
+
+  DISALLOW_COPY_AND_ASSIGN(ResetOnLoadObserverImpl);
+};
+
 }  // namespace
 
 namespace chrome_prefs {
@@ -428,8 +451,7 @@ std::unique_ptr<PrefService> CreateLocalState(
 
 std::unique_ptr<sync_preferences::PrefServiceSyncable> CreateProfilePrefs(
     const base::FilePath& profile_path,
-    base::SequencedTaskRunner* pref_io_task_runner,
-    prefs::mojom::TrackedPreferenceValidationDelegate* validation_delegate,
+    prefs::mojom::TrackedPreferenceValidationDelegatePtr validation_delegate,
     policy::PolicyService* policy_service,
     SupervisedUserSettingsService* supervised_user_settings,
     const scoped_refptr<PrefStore>& extension_prefs,
@@ -439,22 +461,17 @@ std::unique_ptr<sync_preferences::PrefServiceSyncable> CreateProfilePrefs(
   TRACE_EVENT0("browser", "chrome_prefs::CreateProfilePrefs");
   SCOPED_UMA_HISTOGRAM_TIMER("PrefService.CreateProfilePrefsTime");
 
-  // A StartSyncFlare used to kick sync early in case of a reset event. This is
-  // done since sync may bring back the user's server value post-reset which
-  // could potentially cause a "settings flash" between the factory default and
-  // the re-instantiated server value. Starting sync ASAP minimizes the window
-  // before the server value is re-instantiated (this window can otherwise be
-  // as long as 10 seconds by default).
-  const base::Closure start_sync_flare_for_prefs =
-      base::Bind(sync_start_util::GetFlareForSyncableService(profile_path),
-                 syncer::PREFERENCES);
-
+  prefs::mojom::ResetOnLoadObserverPtr reset_on_load_observer;
+  mojo::MakeStrongBinding(
+      base::MakeUnique<ResetOnLoadObserverImpl>(profile_path),
+      mojo::MakeRequest(&reset_on_load_observer));

[gab, 2017/04/03 16:11:17]

General Mojo question (since I can't find documentation for this either): what
does this do? And how would I know to write this as a non-mojo guru?

i.e. why aren't we just passing
base::MakeUnique<ResetOnLoadObserverImpl>(profile_path) in
CreateProfilePrefStore() below?

[Sam McNally, 2017/04/04 03:24:49]

There are docs for this now:
https://chromium.googlesource.com/chromium/src/+/master/mojo/public/cpp/bindi....
In particular, this is the pattern described in
https://chromium.googlesource.com/chromium/src/+/master/mojo/public/cpp/bindi....

We want to pass to the service the client end of a mojo pipe pointing at the
ResetOnLoadObserverImpl (in this case using a StrongBinding to manage the impl
lifetime).

[gab, 2017/04/04 20:59:51]

Awesome, thanks!

PS: Guess this is easy now as this OnResetOnLoad() override makes a static call,
but lifetime would be more complex if that object needed to  be teared down
before something else it owned, right? What would you do then? Refcount its
state?

[Sam McNally, 2017/04/05 00:44:30]

Probably something like how it was managed before: ProfileImpl would own both
the implementation and a Binding. Then when the shared state goes away, the mojo
connection would break.

   sync_preferences::PrefServiceSyncableFactory factory;
   scoped_refptr<PersistentPrefStore> user_pref_store(
       CreateProfilePrefStoreManager(profile_path)
-          ->CreateProfilePrefStore(
-              pref_io_task_runner, start_sync_flare_for_prefs,
-              validation_delegate, connector, pref_registry));
+          ->CreateProfilePrefStore(content::BrowserThread::GetBlockingPool(),
+                                   std::move(reset_on_load_observer),
+                                   std::move(validation_delegate), connector,
+                                   pref_registry));
   PrepareFactory(&factory, profile_path, policy_service,
                  supervised_user_settings, user_pref_store, extension_prefs,
                  async);