Move history API out of experimental. Allow extensions to override history page.

chrome/common/extensions/extension_constants.h

 // Copyright (c) 2009 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 CHROME_COMMON_EXTENSIONS_EXTENSION_CONSTANTS_H_
 #define CHROME_COMMON_EXTENSIONS_EXTENSION_CONSTANTS_H_
 
 // Keys used in JSON representation of extensions.
 namespace extension_manifest_keys {
   extern const wchar_t* kAllFrames;
@@ skipping 126 matching lines @@
   extern const char* kInvalidThemeTints;
   extern const char* kInvalidWebContentEnabled;
   extern const char* kInvalidWebOrigin;
   extern const char* kInvalidWebPaths;
   extern const char* kInvalidWebPath;
   extern const char* kOneUISurfaceOnly;
   extern const char* kThemesCannotContainExtensions;
   extern const char* kManifestParseError;
   extern const char* kManifestUnreadable;
   extern const char* kMissingFile;
+  extern const char* kMultipleOverrides;
   extern const char* kInvalidUpdateURL;
   extern const char* kInvalidDefaultLocale;
   extern const char* kLaunchContainerWithoutURL;
   extern const char* kLaunchPathAndURLAreExclusive;
   extern const char* kLocalesNoDefaultLocaleSpecified;
   extern const char* kLocalesNoDefaultMessages;
   extern const char* kLocalesNoValidLocaleNamesListed;
   extern const char* kLocalesTreeMissing;
   extern const char* kLocalesMessagesFileMissing;
   extern const char* kInvalidOptionsPage;
   extern const char* kReservedMessageFound;
   extern const char* kCannotAccessPage;
   extern const char* kCannotScriptGallery;
   extern const char* kWebContentMustBeEnabled;
 }  // namespace extension_manifest_errors
 
 namespace extension_urls {
   // The greatest common prefixes of the main extensions gallery's browse and
   // download URLs.
   extern const char* kGalleryBrowsePrefix;
   extern const char* kGalleryDownloadPrefix;
 
   // Same thing for the "minigallery". The minigallery is the temporary static
   // themes gallery that we put up when we launched themes.
   extern const char* kMiniGalleryBrowsePrefix;
   extern const char* kMiniGalleryDownloadPrefix;
 }  // namespace extension_urls
 
 #endif  // CHROME_COMMON_EXTENSIONS_EXTENSION_CONSTANTS_H_