Adding pref to store the user-selected proximity threshold.

chrome/app/settings_strings.grdp

Index: chrome/app/settings_strings.grdp
diff --git a/chrome/app/settings_strings.grdp b/chrome/app/settings_strings.grdp
index bcc5c414d31ef420b2f3a18370cfb6cb3840fc2a..ccf0648b16d07be9b3b5e596eb8d7d1c9de55344 100644
--- a/chrome/app/settings_strings.grdp
+++ b/chrome/app/settings_strings.grdp
@@ -1106,6 +1106,21 @@
     <message name="IDS_SETTINGS_EASY_UNLOCK_TURN_OFF_RETRY" desc="The label text of the retry button on the Easy unlock turn off dialog when Easy unlock could not be turned off because there is a server error.">
       Retry
     </message>
+    <message name="IDS_SETTINGS_EASY_UNLOCK_PROXIMITY_THRESHOLD_LABEL" desc="The text on the Easy unlock settings page indicating how close the phone should be for unlock to work.">
+      Only unlock this Chromebook when your phone is
+    </message>
+    <message name="IDS_SETTINGS_EASY_UNLOCK_PROXIMITY_THRESHOLD_VERY_CLOSE" desc="The text on the Easy unlock settings page indicating the phone should be very close for the unlock to work.">
+      very close
+    </message>
+    <message name="IDS_SETTINGS_EASY_UNLOCK_PROXIMITY_THRESHOLD_CLOSE" desc="The text on the Easy unlock settings page indicating the phone should be close for the unlock to work.">
+      close
+    </message>
+    <message name="IDS_SETTINGS_EASY_UNLOCK_PROXIMITY_THRESHOLD_FAR" desc="The text on the Easy unlock settings page indicating the phone can far for the unlock to work.">

[Tim Song, 2017/07/07 21:48:24]

nit: can be far

[sacomoto, 2017/07/10 16:54:07]

Done.

+      far
+    </message>
+    <message name="IDS_SETTINGS_EASY_UNLOCK_PROXIMITY_THRESHOLD_VERY_FAR" desc="The text on the Easy unlock settings page indicating the phone can be very far for the unlock to work.">
+      very far
+    </message>
 
     <!-- Strings specific to the Settings Internet Page -->
     <message name="IDS_SETTINGS_INTERNET" desc="Name of the settings page which displays internet preferences.">