--downloads-new-ui completely disables the download shelf.

chrome/app/generated_resources.grd

Index: chrome/app/generated_resources.grd
diff --git a/chrome/app/generated_resources.grd b/chrome/app/generated_resources.grd
index bc48cad224d8ea05ee0f32294e129ec300708100..4664c02bd31357eaa772dbd5e3efac5ea4882310 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -4230,6 +4230,12 @@ Keep your key file in a safe place. You will need it to create new versions of y
       <message name="IDS_FLAGS_MEMORY_WIDGET_DESCRIPTION" desc="Description of the 'Show memory status' lab.">
         Shows the amount of free memory in the status area. Click on the menu for more information about system memory.
       </message>      
+      <message name="IDS_FLAGS_DOWNLOADS_NEW_UI_NAME" desc="Title for the flag to replace the download shelf with an experimental new UI.">

[cbentzel, 2011/08/15 18:28:26]

Nit: I recommend replacing with

"Name of the 'New Downloads UI' lab."

to be more consistent with the rest of this file.

[benjhayden, 2011/08/15 19:15:36]

Done.

+        New Downloads UI
+      </message>
+      <message name="IDS_FLAGS_DOWNLOADS_NEW_UI_DESCRIPTION" desc="Description for the flag to replace the download shelf with an experimental new UI.">

[cbentzel, 2011/08/15 18:28:26]

Nit: I recommend replacing with

"Description of the 'New Downloads UI' lab."

to be more consistent with the rest of this file.

[benjhayden, 2011/08/15 19:15:36]

Done.

+        Show an experimental new UI instead of the download shelf.

[Peter Kasting, 2011/08/15 18:34:02]

Nit: Show -> Shows, for consistency with elsewhere

[benjhayden, 2011/08/15 19:15:36]

Done.

+      </message>
       <message name="IDS_FLAGS_XSS_AUDITOR_NAME" desc="Description of the 'XSS Auditor' lab.">
         XSS Auditor
       </message>