Policy: Add ProxyMode and deprecate ProxyServerMode.

chrome/browser/prefs/proxy_prefs.h

Index: chrome/browser/prefs/proxy_prefs.h
diff --git a/chrome/browser/prefs/proxy_prefs.h b/chrome/browser/prefs/proxy_prefs.h
index bbeb44d79901bda686a58bb71391859a97152c2f..da911d4e857db21329aaf8286ee7bd590d984008 100644
--- a/chrome/browser/prefs/proxy_prefs.h
+++ b/chrome/browser/prefs/proxy_prefs.h
@@ -36,6 +36,14 @@ enum ProxyMode {
   kModeCount
 };
 
+// Constants for string values used to specify the proxy mode through externally
+// visible APIs, e.g. through policy or the proxy extension API.
+extern const char kDirectProxyModeName[];
+extern const char kAutoDetectProxyModeName[];
+extern const char kPacScriptProxyModeName[];
+extern const char kFixedServersProxyModeName[];
+extern const char kSystemProxyModeName[];
+
 bool IntToProxyMode(int in_value, ProxyMode* out_value);
 bool StringToProxyMode(const std::string& in_value,
                        ProxyMode* out_value);