First pass at experimental omnibox API. There are plenty of rough edges and

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 46 matching lines @@
   extern const wchar_t* kToolstrips;
   extern const wchar_t* kType;
   extern const wchar_t* kVersion;
   extern const wchar_t* kUpdateURL;
   extern const wchar_t* kOptionsPage;
   extern const wchar_t* kWebContent;
   extern const wchar_t* kWebContentEnabled;
   extern const wchar_t* kWebLaunchUrl;
   extern const wchar_t* kWebOrigin;
   extern const wchar_t* kWebPaths;
+  extern const wchar_t* kOmniboxKeyword;
 }  // namespace extension_manifest_keys
 
 // Some values expected in manifests.
 namespace extension_manifest_values {
   extern const char* kRunAtDocumentStart;
   extern const char* kRunAtDocumentEnd;
   extern const char* kRunAtDocumentIdle;
   extern const char* kPageActionTypeTab;
   extern const char* kPageActionTypePermanent;
   extern const char* kLaunchContainerPanel;
@@ skipping 77 matching lines @@
   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;
+  extern const char* kInvalidOmniboxKeyword;
+  extern const char* kOmniboxExperimental;
 }  // 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.
@@ skipping 12 matching lines @@
   // The file to write our decoded message catalogs to, relative to the
   // extension_path.
   extern const char* kDecodedMessageCatalogsFilename;
 }
 
 namespace extension_misc {
   const int kUnknownWindowId = -1;
 }  // extension_misc
 
 #endif  // CHROME_COMMON_EXTENSIONS_EXTENSION_CONSTANTS_H_