NOT YET READY: UMA recording the kind of target frame when extensions pierce browsing instance.

extensions/common/view_type.h

 // 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.
 
 #ifndef EXTENSIONS_COMMON_VIEW_TYPE_H_
 #define EXTENSIONS_COMMON_VIEW_TYPE_H_
 
 namespace extensions {
 
 // Icky RTTI used by a few systems to distinguish the host type of a given
 // WebContents.
 //
+// Do not change the order of entries or remove entries in this list as this
+// is used in ExtensionViewType enum in tools/metrics/histograms/enums.xml.
+//
 // TODO(aa): Remove this and teach those systems to keep track of their own
 // data.
 enum ViewType {
-  VIEW_TYPE_INVALID,
-  VIEW_TYPE_APP_WINDOW,
-  VIEW_TYPE_BACKGROUND_CONTENTS,
-  VIEW_TYPE_COMPONENT,  // For custom parts of Chrome if no other type applies.
-  VIEW_TYPE_EXTENSION_BACKGROUND_PAGE,
-  VIEW_TYPE_EXTENSION_DIALOG,
-  VIEW_TYPE_EXTENSION_GUEST,
-  VIEW_TYPE_EXTENSION_POPUP,
-  VIEW_TYPE_LAUNCHER_PAGE,
-  VIEW_TYPE_PANEL,
-  VIEW_TYPE_TAB_CONTENTS,
-  VIEW_TYPE_LAST = VIEW_TYPE_TAB_CONTENTS
+  VIEW_TYPE_INVALID = 0,
+  VIEW_TYPE_APP_WINDOW = 1,
+  VIEW_TYPE_BACKGROUND_CONTENTS = 2,
+
+  // For custom parts of Chrome if no other type applies.
+  VIEW_TYPE_COMPONENT = 3,
+
+  VIEW_TYPE_EXTENSION_BACKGROUND_PAGE = 4,
+  VIEW_TYPE_EXTENSION_DIALOG = 5,
+  VIEW_TYPE_EXTENSION_GUEST = 6,
+  VIEW_TYPE_EXTENSION_POPUP = 7,
+  VIEW_TYPE_LAUNCHER_PAGE = 8,
+  VIEW_TYPE_PANEL = 9,
+  VIEW_TYPE_TAB_CONTENTS = 10,
+
+  VIEW_TYPE_LAST = VIEW_TYPE_TAB_CONTENTS,
 };
 
 // Constant strings corresponding to the Type enumeration values.  Used
 // when converting JS arguments.
 extern const char kViewTypeAll[];
 extern const char kViewTypeAppWindow[];
 extern const char kViewTypeBackgroundPage[];
 extern const char kViewTypeExtensionDialog[];
 extern const char kViewTypeLauncherPage[];
 extern const char kViewTypePanel[];
 extern const char kViewTypePopup[];
 extern const char kViewTypeTabContents[];
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_VIEW_TYPE_H_