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

chrome/app/chromeos_strings.grdp

Index: chrome/app/chromeos_strings.grdp
diff --git a/chrome/app/chromeos_strings.grdp b/chrome/app/chromeos_strings.grdp
index 7bc7d3041a84eea86cb86516bc451cda2da70c4a..9f5b950a88f93a4164d2a78ae8665ac494d6959b 100644
--- a/chrome/app/chromeos_strings.grdp
+++ b/chrome/app/chromeos_strings.grdp
@@ -91,6 +91,12 @@ Press any key to continue exploring.
   <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>