Adding pref to store the user-selected proximity threshold.

components/proximity_auth/proximity_auth_pref_manager.h

Index: components/proximity_auth/proximity_auth_pref_manager.h
diff --git a/components/proximity_auth/proximity_auth_pref_manager.h b/components/proximity_auth/proximity_auth_pref_manager.h
index 9f74191417fc2f6efe8823ad2e81f4e26085ead1..08540218035184f71fe1cfbac281996893c98955 100644
--- a/components/proximity_auth/proximity_auth_pref_manager.h
+++ b/components/proximity_auth/proximity_auth_pref_manager.h
@@ -65,6 +65,22 @@ class ProximityAuthPrefManager {
   virtual void SetLastPasswordEntryTimestampMs(int64_t timestamp_ms);
   virtual int64_t GetLastPasswordEntryTimestampMs() const;
 
+  // These are arbitrary labels displayed in the settings page for the user
+  // to select. The actual mapping is done in the ProximityMonitorImpl.
+  enum ProximityThreshold {
+    kVeryClose = 0,
+    kClose = 1,
+    kFar = 2,
+    kVeryFar = 3
+  };
+
+  // Setter and getter for the proximity threshold. This preference is
+  // exposed to the user, allowing him / her to change how close the
+  // phone must for the unlock to be allowed.
+  // Note: These are arbitrary values,
+  virtual void SetProximityThreshold(ProximityThreshold value);
+  virtual ProximityThreshold GetProximityThreshold() const;
+
  private:
   const base::DictionaryValue* GetRemoteBleDevices() const;