cros: Implement cryptohome backend for pin.

chrome/browser/chromeos/extensions/quick_unlock_private/quick_unlock_private_api.h

Index: chrome/browser/chromeos/extensions/quick_unlock_private/quick_unlock_private_api.h
diff --git a/chrome/browser/chromeos/extensions/quick_unlock_private/quick_unlock_private_api.h b/chrome/browser/chromeos/extensions/quick_unlock_private/quick_unlock_private_api.h
index 34aac6a150a497ace0db4f960a7979a59c73b184..0c1bcb2bfddf8fd089175d65240a433424998c5c 100644
--- a/chrome/browser/chromeos/extensions/quick_unlock_private/quick_unlock_private_api.h
+++ b/chrome/browser/chromeos/extensions/quick_unlock_private/quick_unlock_private_api.h
@@ -51,6 +51,9 @@ class QuickUnlockPrivateGetActiveModesFunction
   ResponseAction Run() override;
 
  private:
+  void OnGetActiveModes(
+      const std::vector<api::quick_unlock_private::QuickUnlockMode>& modes);
+
   ChromeExtensionFunctionDetails chrome_details_;
 
   DISALLOW_COPY_AND_ASSIGN(QuickUnlockPrivateGetActiveModesFunction);
@@ -127,7 +130,14 @@ class QuickUnlockPrivateSetModesFunction : public UIThreadExtensionFunction,
   void OnAuthFailure(const chromeos::AuthFailure& error) override;
   void OnAuthSuccess(const chromeos::UserContext& user_context) override;
 
-  void ApplyModeChange();
+  // Continuation of OnAuthSuccess after active modes have been fetched.
+  void OnGetActiveModesAfterAuthSuccess(
+      const chromeos::UserContext& user_context,
+      const std::vector<api::quick_unlock_private::QuickUnlockMode>& modes);
+
+  // Apply any changes specified in |params_|. Returns the new active modes.
+  std::vector<api::quick_unlock_private::QuickUnlockMode> ApplyModeChange(

[achuithb, 2017/05/13 01:01:57]

Is it worthwhile using a typedef for this?

[jdufault, 2017/06/06 18:17:06]

Done.

+      const chromeos::UserContext& user_context);
 
  private:
   void FireEvent(const std::vector<QuickUnlockMode>& modes);