Add --disable-panels for blocking all extensions from using panels.

chrome/browser/about_flags.cc

 // Copyright (c) 2012 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 <iterator>
 #include <map>
 #include <set>
 #include <utility>
@@ skipping 647 matching lines @@
      // Uses the system preference on Mac (a different implementation).
      // On Android, this is always enabled.
      kOsLinux | kOsCrOS | kOsWin,
      ENABLE_DISABLE_VALUE_TYPE(switches::kEnableOverlayScrollbar,
                                switches::kDisableOverlayScrollbar)},
 #endif
     {"enable-panels",
      IDS_FLAGS_PANELS_NAME,
      IDS_FLAGS_PANELS_DESCRIPTION,
      kOsDesktop,
-     SINGLE_VALUE_TYPE(switches::kEnablePanels)},
+     ENABLE_DISABLE_VALUE_TYPE(switches::kEnablePanels,
+                               switches::kDisablePanels)},
     {// See http://crbug.com/120416 for how to remove this flag.
      "save-page-as-mhtml",  // FLAGS:RECORD_UMA
      IDS_FLAGS_SAVE_PAGE_AS_MHTML_NAME,
      IDS_FLAGS_SAVE_PAGE_AS_MHTML_DESCRIPTION,
      kOsMac | kOsWin | kOsLinux,
      SINGLE_VALUE_TYPE(switches::kSavePageAsMHTML)},
     {"enable-quic",
      IDS_FLAGS_QUIC_NAME,
      IDS_FLAGS_QUIC_DESCRIPTION,
      kOsAll,
@@ skipping 1613 matching lines @@
 const base::HistogramBase::Sample kBadSwitchFormatHistogramId = 0;
 
 const FeatureEntry* GetFeatureEntries(size_t* count) {
   *count = arraysize(kFeatureEntries);
   return kFeatureEntries;
 }
 
 }  // namespace testing
 
 }  // namespace about_flags