Implement BrowserStateKeyedServiceFactory::GetAssociatedPrefRegistry()

components/keyed_service/ios/browser_state_keyed_service_factory.cc

Index: components/keyed_service/ios/browser_state_keyed_service_factory.cc
diff --git a/components/keyed_service/ios/browser_state_keyed_service_factory.cc b/components/keyed_service/ios/browser_state_keyed_service_factory.cc
index 115569281ab70ffd11eeed4791b7ecf7d67e03a4..3d2b751fc3934c01aa8a2bc305b2ec89d2ed0044 100644
--- a/components/keyed_service/ios/browser_state_keyed_service_factory.cc
+++ b/components/keyed_service/ios/browser_state_keyed_service_factory.cc
@@ -5,9 +5,12 @@
 #include "components/keyed_service/ios/browser_state_keyed_service_factory.h"
 
 #include "base/logging.h"
+#include "base/prefs/pref_service.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "components/keyed_service/ios/browser_state_dependency_manager.h"
 #include "components/keyed_service/ios/browser_state_helper.h"
+#include "components/pref_registry/pref_registry_syncable.h"
+#include "components/user_prefs/user_prefs.h"
 #include "ios/web/public/browser_state.h"
 
 void BrowserStateKeyedServiceFactory::SetTestingFactory(
@@ -87,8 +90,14 @@ bool BrowserStateKeyedServiceFactory::IsOffTheRecord(
 user_prefs::PrefRegistrySyncable*
 BrowserStateKeyedServiceFactory::GetAssociatedPrefRegistry(
     base::SupportsUserData* context) const {
-  NOTREACHED();
-  return nullptr;
+  // TODO(droger): Move this code to KeyedServiceFactory and share it with the
+  // other platforms once iOS no longer needs BrowserStateFromContext().
+  PrefService* prefs =
+      user_prefs::UserPrefs::Get(BrowserStateFromContext(context));

[Bernhard Bauer, 2015/04/15 15:28:13]

Why is the call to BrowserStateFromContext necessary if UserPrefs::Get now takes
a base::SupportsUserData?

[droger, 2015/04/15 15:33:08]

This is because we currently are in a temporary state where we have both
BrowserContext keyed services and BrowserState keyed services downstream, and
they depend on each other.

We're trying to remove all the BrowserContext references from our downstream
code, but meanwhile we need these hacks.
Eventually we won't need this anymore.

[droger, 2015/04/15 15:37:07]

Also: BrowserStateFromContext() returns base::SupportsUserData.

[Bernhard Bauer, 2015/04/15 15:39:54]

Yes, that was what confused me :) For the content/ equivalent, it's just a
static cast.

+  user_prefs::PrefRegistrySyncable* registry =
+      static_cast<user_prefs::PrefRegistrySyncable*>(
+          prefs->DeprecatedGetPrefRegistry());
+  return registry;
 }
 
 base::SupportsUserData* BrowserStateKeyedServiceFactory::GetContextToUse(