Adding --disable-plugins-discovery command line switch to not load third-party plugins from common …

webkit/plugins/npapi/plugin_list_posix.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 "webkit/plugins/npapi/plugin_list.h"
 
 #include <algorithm>
 #include <dlfcn.h>
 #if defined(OS_OPENBSD)
 #include <sys/exec_elf.h>
@@ skipping 418 matching lines @@
     info->version = UTF8ToUTF16(version);
   }
 }
 
 void PluginList::GetPluginDirectories(std::vector<base::FilePath>* plugin_dirs) {
   // See http://groups.google.com/group/chromium-dev/browse_thread/thread/7a70e5fcbac786a9
   // for discussion.
   // We first consult Chrome-specific dirs, then fall back on the logic
   // Mozilla uses.
 
-  // Note: "extra" plugin dirs, including the Plugins subdirectory of
-  // your Chrome config, are examined before these.  See the logic
-  // related to extra_plugin_dirs in plugin_list.cc.
+  if (PluginList::plugins_discovery_disabled_)
+    return;
+
+  // Note: "extra" plugin dirs and paths are examined before these.
+  // "Extra" are those added by PluginList::AddExtraPluginDir() and
+  // PluginList::AddExtraPluginPath().
 
   // The Chrome binary dir + "plugins/".
   base::FilePath dir;
   PathService::Get(base::DIR_EXE, &dir);
   plugin_dirs->push_back(dir.Append("plugins"));
 
   // Chrome OS only loads plugins from /opt/google/chrome/plugins.
 #if !defined(OS_CHROMEOS)
   // Mozilla code to reference:
   // http://mxr.mozilla.org/firefox/ident?i=NS_APP_PLUGINS_DIR_LIST
@@ skipping 133 matching lines @@
 
   // TODO(evanm): prefer the newest version of flash, etc. here?
 
   VLOG_IF(1, PluginList::DebugPluginLoading()) << "Using " << info.path.value();
 
   return true;
 }
 
 }  // namespace npapi
 }  // namespace webkit