Add chrome-search: access from Instant overlay

chrome/common/url_constants.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.
 
 // Contains constants for known URLs and portions thereof.
 
 #ifndef CHROME_COMMON_URL_CONSTANTS_H_
 #define CHROME_COMMON_URL_CONSTANTS_H_
 
 #include "build/build_config.h"
@@ skipping 393 matching lines @@
 extern const char kLearnMoreEnterpriseURL[];
 #endif
 
 // "Debug" pages which are dangerous and not for general consumption.
 extern const char* const kChromeDebugURLs[];
 extern const int kNumberOfChromeDebugURLs;
 
 // Canonical schemes you can use as input to GURL.SchemeIs().
 extern const char kExtensionResourceScheme[];
 
+// The chrome-search: scheme is served by the same backend as chrome:.  However,
+// only specific URLDataSources are enabled to serve requests via the
+// chrome-search: scheme.  See |InstantIOContext::ShouldServiceRequest| and its
+// callers for details.  Note that WebUIBindings should never be granted to
+// chrome-search: pages.
 extern const char kChromeSearchScheme[];
 
 #if defined(OS_CHROMEOS)
 extern const char kCrosScheme[];
 extern const char kDriveScheme[];
 
 // "Learn more" URL for the Cloud Print section under Options.
 extern const char kCloudPrintLearnMoreURL[];
 #endif
 
 // Parameters that get appended to force SafeSearch.
 extern const char kSafeSearchSafeParameter[];
 extern const char kSafeSearchSsuiParameter[];
 
 // The URL for the "Learn more" link in the media access infobar.
 extern const char kMediaAccessLearnMoreUrl[];
 
 }  // namespace chrome
 
 #endif  // CHROME_COMMON_URL_CONSTANTS_H_