Remove a flag to show storage manager in options page.

chrome/app/chromeos_strings.grdp

 <?xml version="1.0" encoding="utf-8"?>
 <!-- ChromeOS-specific strings (included from generated_resources.grd).
      Everything in this file is wrapped in <if expr="chromeos">. -->
 <grit-part>
   <message name="IDS_EMPTY_STRING" desc="Empty string, exist only to make code generic. No translation required.">
   </message>
   <!-- Idle logout dialog for retail mode -->
   <message name="IDS_IDLE_LOGOUT_TITLE" desc="Dialog title for the idle logout dialog. Used in retail mode only.">
     Are you still there?
   </message>
@@ skipping 1398 matching lines @@
   </message>
   <message name="IDS_FLAGS_MD_STORAGE_MANAGER_DESCRIPTION" desc="Description for the flag to enable experimental storage manager.">
     Enables storage manager in Material Design Settings.
   </message>
   <message name="IDS_FLAGS_QUICK_UNLOCK_PIN" desc="Title of the flag used to enable quick unlock pin.">
     Quick Unlock (PIN)
   </message>
   <message name="IDS_FLAGS_QUICK_UNLOCK_PIN_DESCRIPTION" desc="Description of the flag used to enable quick unlock pin.">
     Enabling PIN quick unlock allows you to use a PIN to unlock your Chromebook on the lock screen after you have signed into your device.
   </message>
-  <message name="IDS_FLAGS_STORAGE_MANAGER_NAME" desc="Description for the flag to enable experimental storage manager.">
-    Storage manager
-  </message>
-  <message name="IDS_FLAGS_STORAGE_MANAGER_DESCRIPTION" desc="Description for the flag to enable experimental storage manager.">
-    Enables storage manager to manage local storage.
-  </message>
   <message name="IDS_OFFERS_CONSENT_INFOBAR_LABEL_LEARN_MORE" desc="Text of the Learn More link in the echo dialog.">
     Learn More
   </message>
   <message name="IDS_OFFERS_CONSENT_INFOBAR_ENABLE_BUTTON" desc="Enable button label.">
     Allow
   </message>
   <message name="IDS_OFFERS_CONSENT_INFOBAR_DISABLE_BUTTON" desc="Disable button label.">
     Deny
   </message>
   <message name="IDS_NETWORK_CONFIG_ERROR_INCORRECT_PASSWORD" desc="Error for network configuration: Incorrect password.">
@@ skipping 4946 matching lines @@
   <message name="IDS_FLAGS_ENABLE_EHV_INPUT_NAME" desc="Name of the about: flag for enabling emoji, handwriting and voice input on opt-in IME menu.">
     Emoji, handwriting and voice input on opt-in IME menu
     </message>
   <message name="IDS_FLAGS_ENABLE_EHV_INPUT_DESCRIPTION" desc="Description of the about: flag enabling emoji, handwriting and voice input on opt-in IME menu.">
     Enable access to emoji, handwriting and voice input form opt-in IME menu.
   </message>
   <message name="IDS_HATS_DONE_BUTTON_LABEL" desc="Label used for the done button at the end of survey">
     Done
   </message>
 </grit-part>