Make CrOS proxy configuration write prefs directly.

net/proxy/proxy_bypass_rules.cc

Index: net/proxy/proxy_bypass_rules.cc
diff --git a/net/proxy/proxy_bypass_rules.cc b/net/proxy/proxy_bypass_rules.cc
index 91c6f447e2d4fcd58b96980a33a7d22f817ec018..dde3d8f482e593b2079e9a59cf8e21f8cdabacdf 100644
--- a/net/proxy/proxy_bypass_rules.cc
+++ b/net/proxy/proxy_bypass_rules.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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.
 
@@ -219,6 +219,17 @@ bool ProxyBypassRules::AddRuleFromStringUsingSuffixMatching(
   return AddRuleFromStringInternalWithLogging(raw, true);
 }
 
+std::string ProxyBypassRules::ToString() const {
+  std::string result;
+  for (RuleList::const_iterator rule(rules_.begin());
+       rule != rules_.end();
+       ++rule) {
+    result += (*rule)->ToString();
+    result += ";";
+  }
+  return result;
+}
+
 void ProxyBypassRules::Clear() {
   STLDeleteElements(&rules_);
 }