Add policy provider that would filter extensions/apps allowed on the

chrome/browser/extensions/extension_system_impl.h

Index: chrome/browser/extensions/extension_system_impl.h
diff --git a/chrome/browser/extensions/extension_system_impl.h b/chrome/browser/extensions/extension_system_impl.h
index 5cd96a310ff1c93fcefe1abbea79f166005cdf8e..236cee2ae8e384f6adb426d47a4db7cd26ac75c9 100644
--- a/chrome/browser/extensions/extension_system_impl.h
+++ b/chrome/browser/extensions/extension_system_impl.h
@@ -15,6 +15,13 @@
 class Profile;
 class ValueStore;
 
+#if defined(OS_CHROMEOS)
+namespace chromeos {
+class DeviceLocalAccountManagementPolicyProvider;
+class SigninScreenPolicyProvider;
+}
+#endif  // defined(OS_CHROMEOS)

[asargent_no_longer_on_chrome, 2016/07/22 00:13:29]

I've been trying to have us move away from using #ifdef's to separate chromeos
parts of code (since that can make things pretty hard to read) in favor of other
approaches like using delegate interfaces, subclasses, listeners, etc.

As an example, in this CL from a while back:

https://codereview.chromium.org/1869483002/diff/1/chrome/browser/extensions/e...

instead of adding more #ifdef chromeos blocks, we instead added a generic
interface:

https://codereview.chromium.org/1890163004

I think we should try and do something similar here.

[Denis Kuznetsov (DE-MUC), 2016/07/22 14:37:14]

That was just a move from extension_system.h.
I agree that adding new #ifdefs complicates the code, but this CL only adds some
code inside already-existing CHROMEOS ifdefs.
And while your suggestion seems very reasonable, I believe that should be the
scope of separate CL (as it would also affect existing code, like
DeviceLocalAccountManagementPolicyProvider).

[asargent_no_longer_on_chrome, 2016/07/25 21:27:01]

It would be fine to do this in a separate CL, but I'd like to see that land
before this one. 

+
 namespace extensions {
 
 class ExtensionSystemSharedFactory;
@@ -134,6 +141,8 @@ class ExtensionSystemImpl : public ExtensionSystem {
 #if defined(OS_CHROMEOS)
     std::unique_ptr<chromeos::DeviceLocalAccountManagementPolicyProvider>
         device_local_account_management_policy_provider_;
+    std::unique_ptr<chromeos::SigninScreenPolicyProvider>
+        signin_screen_policy_provider_;
     std::unique_ptr<InstallGate> kiosk_app_update_install_gate_;
 #endif