Remove implementation of Panels on OSes other than ChromeOS.

chrome/chrome_browser.gypi

 # Copyright 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.
 
 {
   'variables': {
     # All .cc, .h, .m, and .mm files under browser except for:
     # * tests and mocks.
     # * code below browser/chromeos
     # * code below browser/extensions
@@ skipping 3143 matching lines @@
       'browser/task_manager/providers/web_contents/devtools_task.cc',
       'browser/task_manager/providers/web_contents/devtools_task.h',
       'browser/task_manager/providers/web_contents/extension_tag.cc',
       'browser/task_manager/providers/web_contents/extension_tag.h',
       'browser/task_manager/providers/web_contents/extension_task.cc',
       'browser/task_manager/providers/web_contents/extension_task.h',
       'browser/task_manager/providers/web_contents/guest_tag.cc',
       'browser/task_manager/providers/web_contents/guest_tag.h',
       'browser/task_manager/providers/web_contents/guest_task.cc',
       'browser/task_manager/providers/web_contents/guest_task.h',
-      'browser/task_manager/providers/web_contents/panel_tag.cc',
-      'browser/task_manager/providers/web_contents/panel_tag.h',
-      'browser/task_manager/providers/web_contents/panel_task.cc',
-      'browser/task_manager/providers/web_contents/panel_task.h',
       'browser/task_manager/providers/web_contents/prerender_tag.cc',
       'browser/task_manager/providers/web_contents/prerender_tag.h',
       'browser/task_manager/providers/web_contents/prerender_task.cc',
       'browser/task_manager/providers/web_contents/prerender_task.h',
       'browser/task_manager/providers/web_contents/printing_tag.cc',
       'browser/task_manager/providers/web_contents/printing_tag.h',
       'browser/task_manager/providers/web_contents/printing_task.cc',
       'browser/task_manager/providers/web_contents/printing_task.h',
       'browser/task_manager/providers/web_contents/renderer_task.cc',
       'browser/task_manager/providers/web_contents/renderer_task.h',
@@ skipping 1163 matching lines @@
             '../components/components.gyp:rlz',
             '../components/components.gyp:search_engines',
             '../rlz/rlz.gyp:rlz_lib',
             'common',
           ],
         },
       ],
     }],
   ],
 }