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

chrome/browser/about_flags.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/about_flags.h"
 
 #include <algorithm>
 #include <iterator>
 #include <map>
 #include <set>
@@ skipping 346 matching lines @@
     "memory-widget",
     IDS_FLAGS_MEMORY_WIDGET_NAME,
     IDS_FLAGS_MEMORY_WIDGET_DESCRIPTION,
     kOsCrOS,
 #if defined(OS_CHROMEOS)
     // This switch exists only on Chrome OS.
     SINGLE_VALUE_TYPE(switches::kMemoryWidget)
 #else
     SINGLE_VALUE_TYPE("")
 #endif
-  },};
+  },
+  {
+    "disable-download-shelf",  // FLAGS:RECORD_UMA
+    IDS_FLAGS_DISABLE_DOWNLOAD_SHELF_NAME,
+    IDS_FLAGS_DISABLE_DOWNLOAD_SHELF_DESCRIPTION,
+    kOsAll - kOsCrOS,

[cbentzel, 2011/08/10 11:54:54]

Nit: Maybe it's just me, but it feels weird to do this instead of

(kOsAll & ~kOsCros)

[benjhayden, 2011/08/10 17:09:17]

Even better, kOsAll.
If we're reimplementing the UI as an extension, then we can be consistent even
across cros.

+    SINGLE_VALUE_TYPE(switches::kDisableDownloadShelf)
+  },
+};
 
 const Experiment* experiments = kExperiments;
 size_t num_experiments = arraysize(kExperiments);
 
 // Stores and encapsulates the little state that about:flags has.
 class FlagsState {
  public:
   FlagsState() : needs_restart_(false) {}
   void ConvertFlagsToSwitches(PrefService* prefs, CommandLine* command_line);
   bool IsRestartNeededToCommitChanges();
@@ skipping 419 matching lines @@
 }
 
 const Experiment* GetExperiments(size_t* count) {
   *count = num_experiments;
   return experiments;
 }
 
 }  // namespace testing
 
 }  // namespace about_flags