Remove PrefServiceSimple, replacing it with PrefService and PrefRegistrySimple.

chrome/browser/prefs/pref_service.cc

Index: chrome/browser/prefs/pref_service.cc
diff --git a/chrome/browser/prefs/pref_service.cc b/chrome/browser/prefs/pref_service.cc
index 61f54f7f1f36acdf5ca20d96b01ae0cc27764c2c..b780995ed1a09ec2220b392bc1c1059bddf8c3e1 100644
--- a/chrome/browser/prefs/pref_service.cc
+++ b/chrome/browser/prefs/pref_service.cc
@@ -18,6 +18,7 @@
 #include "base/value_conversions.h"
 #include "build/build_config.h"
 #include "chrome/browser/prefs/pref_notifier_impl.h"
+#include "chrome/browser/prefs/pref_registry.h"
 #include "chrome/browser/prefs/pref_value_store.h"
 
 using content::BrowserContext;
@@ -43,16 +44,21 @@ PrefService::PrefService(
     PrefNotifierImpl* pref_notifier,
     PrefValueStore* pref_value_store,
     PersistentPrefStore* user_prefs,
-    DefaultPrefStore* default_store,
+    scoped_ptr<PrefRegistry> pref_registry,
     base::Callback<void(PersistentPrefStore::PrefReadError)>
         read_error_callback,
     bool async)
     : pref_notifier_(pref_notifier),
       pref_value_store_(pref_value_store),
       user_pref_store_(user_prefs),
-      default_store_(default_store),
-      read_error_callback_(read_error_callback) {
+      read_error_callback_(read_error_callback),
+      pref_registry_(pref_registry.Pass()) {
   pref_notifier_->SetPrefService(this);
+
+  pref_registry_->RetrieveDefaults(&default_store_);
+  pref_registry_->pref_service_ = this;
+  RegisterInitialPreferences();
+
   InitFromStorage(async);
 }
 
@@ -300,8 +306,37 @@ void PrefService::AddPrefInitObserver(base::Callback<void(bool)> obs) {
   pref_notifier_->AddInitObserver(obs);
 }
 
+PrefRegistry* PrefService::DeprecatedGetPrefRegistry() const {
+  return pref_registry_.get();
+}
+
+void PrefService::RegisterInitialPreferences() {
+  // Invariant: default_store_ is valid and contains the preferences
+  // registered prior to construction time.
+  for (DefaultPrefStore::const_iterator it = default_store_->begin();
+       it != default_store_->end();
+       ++it) {
+    RegisterPreference(it->first.c_str(), it->second, true);
+  }
+}
+
+// TODO(joi): Once all registration is done before the PrefService is
+// constructed, we can stop exposing a separate RegisterPreference
+// method, and we can simplify the registration logic. Possibly at the
+// same point we can remove UnregisterPreference. For now, because a
+// few remaining places register preferences after PrefService
+// construction, it is better to leave this here and have PrefRegistry
+// delegate to PrefService::RegisterPreference after that
+// point. Otherwise, PrefRegistry would need to control PrefService's
+// default_store_ and user_pref_store_ members, as well as the
+// pref_map_ member for UnregisterPreference.

[Mattias Nissler (ping if slow), 2013/01/25 14:57:11]

The default_store_ it controls already! The user_pref_store_ piece is
unfortunate and the whole MarkNeedsEmptyValue thing seems like a big hack to me.
I just looked at the CL that added it, and I think the proper way of handling
this would have been to fix JsonPrefStore to never discard prefs that are set,
even if empty. I'll think a bit more about this and see whether there's a good
way to get rid of PersistentPrefStore::MarkNeedsEmptyValue().

[Jói, 2013/01/29 16:10:02]

Registration is now fully owned by PrefRegistry. PrefService registers for
registration and unregistration callbacks to update its internal caches when
registration is done after construction time, and on unregistration.

+//
+// We are, however, able to implement the interface we desire in the
+// long term on PrefRegistry, and make this relationship an
+// implementation detail.
 void PrefService::RegisterPreference(const char* path,
-                                     Value* default_value) {
+                                     Value* default_value,
+                                     bool in_default_store) {
   DCHECK(CalledOnValidThread());
 
   // The main code path takes ownership, but most don't. We'll be safe.
@@ -330,8 +365,10 @@ void PrefService::RegisterPreference(const char* path,
   if (needs_empty_value)
     user_pref_store_->MarkNeedsEmptyValue(path);
 
-  // Hand off ownership.
-  default_store_->SetDefaultValue(path, scoped_value.release());
+  if (!in_default_store) {
+    // Hand off ownership.
+    default_store_->SetDefaultValue(path, scoped_value.release());
+  }
 }
 
 void PrefService::UnregisterPreference(const char* path) {
@@ -345,6 +382,10 @@ void PrefService::UnregisterPreference(const char* path) {
   default_store_->RemoveDefaultValue(path);
 }
 
+bool PrefService::AllowPrefRegistrarSimple() const {
+  return true;
+}
+
 void PrefService::ClearPref(const char* path) {
   DCHECK(CalledOnValidThread());