Add an extension bubble explaining which extensions are in dev mode.

extensions/common/feature_switch.h

 // Copyright 2013 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.
 
 #ifndef EXTENSIONS_COMMON_FEATURE_SWITCH_H_
 #define EXTENSIONS_COMMON_FEATURE_SWITCH_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 
 class CommandLine;
 
 namespace extensions {
 
 // A switch that can turn a feature on or off. Typically controlled via
 // command-line switches but can be overridden, e.g., for testing.
 class FeatureSwitch {
  public:
   static FeatureSwitch* easy_off_store_install();
+  static FeatureSwitch* force_dev_mode_highlighting();
   static FeatureSwitch* global_commands();
   static FeatureSwitch* script_badges();
   static FeatureSwitch* script_bubble();
   static FeatureSwitch* prompt_for_external_extensions();
   static FeatureSwitch* error_console();
   static FeatureSwitch* enable_override_bookmarks_ui();
 
   enum DefaultValue {
     DEFAULT_ENABLED,
     DEFAULT_DISABLED
@@ skipping 40 matching lines @@
   const char* switch_name_;
   bool default_value_;
   OverrideValue override_value_;
 
   DISALLOW_COPY_AND_ASSIGN(FeatureSwitch);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_FEATURE_SWITCH_H_