Add an extension override bubble and warning box for proxy extensions.

chrome/browser/resources/options/browser_options.js

Index: chrome/browser/resources/options/browser_options.js
diff --git a/chrome/browser/resources/options/browser_options.js b/chrome/browser/resources/options/browser_options.js
index 5bbd7f092ee73116bba45cb5cbd71dd6fc6fed03..a0cee2eec9e68f964237881eddeb69501979330a 100644
--- a/chrome/browser/resources/options/browser_options.js
+++ b/chrome/browser/resources/options/browser_options.js
@@ -570,6 +570,9 @@ cr.define('options', function() {
       this.addExtensionControlledBox_('newtab-section-content',
                                       'newtab-controlled',
                                       false);
+      this.addExtensionControlledBox_('proxy-section-content',
+                                      'proxy-controlled',
+                                      true);
 
       document.body.addEventListener('click', function(e) {
         var button = findAncestor(e.target, function(el) {
@@ -1507,9 +1510,7 @@ cr.define('options', function() {
     setupProxySettingsSection_: function(disabled, extensionControlled) {
       if (!cr.isChromeOS) {
         $('proxiesConfigureButton').disabled = disabled;
-        $('proxiesLabel').textContent =
-            loadTimeData.getString(extensionControlled ?
-                'proxiesLabelExtension' : 'proxiesLabelSystem');
+        $('proxiesLabel').hidden = extensionControlled;
       }
     },
 
@@ -1619,6 +1620,15 @@ cr.define('options', function() {
                                          'newtab-controlled',
                                          details.newTabPage.id,
                                          details.newTabPage.name);
+      this.toggleExtensionControlledBox_('proxy-section-content',
+                                         'proxy-controlled',
+                                         details.proxy.id,
+                                         details.proxy.name);
+
+      // The proxy section contains just the warning box and nothing else, so
+      // if we're hiding the proxy warning box, we should also hide its header
+      // section.
+      $('proxy-section').hidden = details.proxy.id.length == 0;
     },