[unpacker] Add a disable flag for the new zip unpacker.

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>
   <message name="IDS_CHROMEBOOK" desc="The localized name for Chromebook.">
     Chromebook
   </message>
   <message name="IDS_CHROMEBOX" desc="The localized name for Chromebox">
@@ skipping 73 matching lines @@
   </message>
   <message name="IDS_FLAGS_ENABLE_FILE_MANAGER_MTP_DESCRIPTION" desc="Description of the about:flag option to the enable MTP support in file manager.">
     Show MTP devices as a file storage in the file manager.
   </message>
   <message name="IDS_FLAGS_ENABLE_VIDEO_PLAYER_CHROMECAST_SUPPORT_NAME" desc="Name of the about:flag option to enable the chromecast support for video app.">
     Experimental Chromecast support for Video Player
   </message>
   <message name="IDS_FLAGS_ENABLE_VIDEO_PLAYER_CHROMECAST_SUPPORT_DESCRIPTION" desc="Description of the about:flag option to the enable the chromecast support for video app.">
     This option enables experimental Chromecast support for Video Player app on ChromeOS.
   </message>
+  <message name="IDS_FLAGS_DISABLE_NEW_ZIP_UNPACKER_NAME" desc="Name of about::flags option to enable the new ZIP unpacker based on the File System Provider API.">
+    Enable the new ZIP unpacker.
+  </message>
+  <message name="IDS_FLAGS_DISABLE_NEW_ZIP_UNPACKER_DESCRIPTION" desc="Description of about::flags option to enable the new ZIP unpacker based on the File System Provider API.">
+    Enable the new ZIP unpacker flow, based on the File System Provider API.
+  </message>
   <message name="IDS_FILE_SYSTEM_PROVIDER_UNRESPONSIVE_WARNING" desc="A warning shown in a notification that an operation is taking longer than expected.">
     An operation is taking longer than expected. Do you want to abort it?
   </message>
   <message name="IDS_FILE_SYSTEM_PROVIDER_MANY_UNRESPONSIVE_WARNING" desc="A warning shown in a notification that more than one operations are taking longer than expected.">
     Some operations are taking longer than expected. Do you want to abort them?
   </message>
   <message name="IDS_FILE_SYSTEM_PROVIDER_UNRESPONSIVE_ABORT_BUTTON" desc="Label of the button on the notification about an operation(s) taking to long.">
     Abort
   </message>
   <message name="IDS_FILE_BROWSER_ARCHIVE_DIRECTORY_LABEL" desc="/archive directory label.">
@@ skipping 5865 matching lines @@
   <message name="IDS_SET_TIME_BUTTON_CLOSE" desc="Text for the button to close the window.">
     Done
   </message>
   <message name="IDS_SET_TIME_DATE_LABEL" desc="Label for the date input element.">
     System date
   </message>
   <message name="IDS_SET_TIME_TIME_LABEL" desc="Label for the time input element.">
     System time
   </message>
 </grit-part>