Moved the following IPC messages used by the chrome NPAPI plugin installer out of content

chrome/default_plugin/default_plugin.gyp

 # 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.
 
 {
   'variables': {
     'chromium_code': 1,
    },
   'targets': [
     {
@@ skipping 14 matching lines @@
         '<(DEPTH)',
         '<(DEPTH)/third_party/wtl/include',
       ],
       'sources': [
         'plugin_impl_gtk.cc',
         'plugin_impl_gtk.h',
         'plugin_impl_mac.h',
         'plugin_impl_mac.mm',
         'plugin_impl_win.cc',
         'plugin_impl_win.h',
+        'plugin_installer_base.cc',
+        'plugin_installer_base.h',      
         'plugin_main.cc',
         'plugin_main.h',
       ],
       'conditions': [
          ['OS=="win"', {
             'link_settings': {
               'libraries': ['-lurlmon.lib'],
             },
             'sources': [
               'default_plugin_resources.h',
@@ skipping 26 matching lines @@
           'variables': {
             'grit_grd_file': 'default_plugin_resources.grd',
           },
           'includes': [ '../../build/grit_action.gypi' ],
         },
       ],
       'includes': [ '../../build/grit_target.gypi' ],
     },
   ],
 }