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

chrome/common/extensions/extension_constants.cc

 // 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.
 
 #include "chrome/common/extensions/extension_constants.h"
 
 namespace extension_manifest_keys {
 
 const wchar_t* kAllFrames = L"all_frames";
 const wchar_t* kBackground = L"background_page";
@@ skipping 44 matching lines @@
 const wchar_t* kToolstripPath = L"path";
 const wchar_t* kToolstrips = L"toolstrips";
 const wchar_t* kType = L"type";
 const wchar_t* kVersion = L"version";
 const wchar_t* kUpdateURL = L"update_url";
 const wchar_t* kOptionsPage = L"options_page";
 const wchar_t* kWebContent = L"web_content";
 const wchar_t* kWebContentEnabled = L"web_content.enabled";
 const wchar_t* kWebOrigin = L"web_content.origin";
 const wchar_t* kWebPaths = L"web_content.paths";
+const wchar_t* kOmniboxKeyword = L"omnibox_keyword";
 }  // namespace extension_manifest_keys
 
 namespace extension_manifest_values {
 const char* kRunAtDocumentStart = "document_start";
 const char* kRunAtDocumentEnd = "document_end";
 const char* kRunAtDocumentIdle = "document_idle";
 const char* kPageActionTypeTab = "tab";
 const char* kPageActionTypePermanent = "permanent";
 const char* kLaunchContainerPanel = "panel";
 const char* kLaunchContainerTab = "tab";
@@ skipping 162 matching lines @@
     "Messages file is missing for locale.";
 const char* kInvalidOptionsPage =
     "Invalid value for 'options_page'.";
 const char* kReservedMessageFound =
     "Reserved key * found in message catalog.";
 const char* kCannotAccessPage = "Cannot access contents of url \"*\". "
     "Extension manifest must request permission to access this host.";
 const char* kCannotScriptGallery = "The extensions gallery cannot be scripted.";
 const char* kWebContentMustBeEnabled = "The 'web_content.enabled' property "
     "must be set to true in order to use any other web content features.";
+const char* kInvalidOmniboxKeyword =
+    "Invalid value for 'omnibox_keyword'.";
+const char* kOmniboxExperimental =
+    "You must request the 'experimental' permission in order to use the"
+    " omnibox API.";
 }  // namespace extension_manifest_errors
 
 namespace extension_urls {
 const char* kGalleryBrowsePrefix = "https://chrome.google.com/extensions";
 const char* kGalleryDownloadPrefix =
     "https://clients2.googleusercontent.com/crx/download";
 const char* kMiniGalleryBrowsePrefix = "https://tools.google.com/chrome/";
 const char* kMiniGalleryDownloadPrefix = "https://dl-ssl.google.com/chrome/";
 }
 
 namespace extension_filenames {
 const char* kTempExtensionName = "CRX_INSTALL";
 
 // The file to write our decoded images to, relative to the extension_path.
 const char* kDecodedImagesFilename = "DECODED_IMAGES";
 
 // The file to write our decoded message catalogs to, relative to the
 // extension_path.
 const char* kDecodedMessageCatalogsFilename = "DECODED_MESSAGE_CATALOGS";
 }