Correctly clear deprecated "proxy" pref set by data reduction proxy.

chrome/browser/net/spdyproxy/data_reduction_proxy_chrome_settings.cc

 // Copyright 2014 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/browser/net/spdyproxy/data_reduction_proxy_chrome_settings.h"
 
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/pref_service.h"
 #include "base/prefs/scoped_user_pref_update.h"
 #include "chrome/browser/browser_process.h"
@@ skipping 12 matching lines @@
 using data_reduction_proxy::Client;
 using data_reduction_proxy::DataReductionProxyParams;
 using data_reduction_proxy::DataReductionProxySettings;
 
 // The Data Reduction Proxy has been turned into a "best effort" proxy,
 // meaning it is used only if the effective proxy configuration resolves to
 // DIRECT for a URL. It no longer can be a ProxyConfig in the proxy preference
 // hierarchy. This method removes the Data Reduction Proxy configuration from
 // prefs, if present. |proxy_pref_name| is the name of the proxy pref.
 void MigrateDataReductionProxyOffProxyPrefs(PrefService* prefs) {
-  DictionaryPrefUpdate update(prefs, prefs::kProxy);
-  base::DictionaryValue* dict = update.Get();
+  base::DictionaryValue* dict =
+      (base::DictionaryValue*) prefs->GetUserPrefValue(prefs::kProxy);
+  if (!dict)
+    return;
+
+  // Clear empty "proxy" dictionary created by a bug. See http://crbug/448172
+  if (dict->empty()) {
+    prefs->ClearPref(prefs::kProxy);
+    return;
+  }
+
   std::string mode;
   if (!dict->GetString("mode", &mode))
     return;
   if (ProxyModeToString(ProxyPrefs::MODE_FIXED_SERVERS) != mode)
     return;
   std::string proxy_server;
   if (!dict->GetString("server", &proxy_server))
     return;
   net::ProxyConfig::ProxyRules proxy_rules;
   proxy_rules.ParseFromString(proxy_server);
   if (!data_reduction_proxy::DataReductionProxyConfigurator::
           ContainsDataReductionProxy(proxy_rules)) {
     return;
   }
-  dict->SetString("mode", ProxyModeToString(ProxyPrefs::MODE_SYSTEM));

[bengr, 2015/02/04 00:09:50]

Should we also clear the pref if we encounter this setting?

[Not at Google. Contact bengr, 2015/02/04 00:44:14]

Safer not to, especially if we are patching this to M41.

As the cl stands, it will remove all "proxy" entries set by data reduction
proxy. Not sure we gain anything by clearing settings set by other components.

Although I do agree that no one should have to set mode to "system" since it is
the default.

-  dict->SetString("server", "");
-  dict->SetString("bypass_list", "");
+  prefs->ClearPref(prefs::kProxy);
 }
 
 DataReductionProxyChromeSettings::DataReductionProxyChromeSettings(
     scoped_ptr<DataReductionProxyParams> params)
     : DataReductionProxySettings(params.Pass()) {
 }
 
 DataReductionProxyChromeSettings::~DataReductionProxyChromeSettings() {
 }
 
@@ skipping 43 matching lines @@
 #elif defined(OS_OPENBSD)
   return Client::CHROME_OPENBSD;
 #elif defined(OS_SOLARIS)
   return Client::CHROME_SOLARIS;
 #elif defined(OS_QNX)
   return Client::CHROME_QNX;
 #else
   return Client::UNKNOWN;
 #endif
 }