webkit: expose webkit branch and revision number in about pages

webkit/glue/user_agent.h

 // Copyright (c) 2010 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 WEBKIT_GLUE_USER_AGENT_H_
 #define WEBKIT_GLUE_USER_AGENT_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 
 namespace webkit_glue {
 
 // Construct the User-Agent header, filling in |result|.
 // The other parameters are workarounds for broken websites:
 // - If mimic_windows is true, produce a fake Windows Chrome string.
 void BuildUserAgent(bool mimic_windows, std::string* result);
 
 // Builds a User-agent compatible string that describes the OS and CPU type.
 std::string BuildOSCpuInfo();
 
-// Returns the WebKit version (major.minor).
+// Returns the WebKit version, in the form "major.minor (branch@revision)".
 std::string GetWebKitVersion();
 
 }  // namespace webkit_glue
 
 #endif  // WEBKIT_GLUE_USER_AGENT_H_