Support persistent incognito preferences

chrome/common/extensions/docs/static/proxy.html

 <div id="pageData-name" class="pageData">Proxy Settings</div>
 
 <!-- BEGIN AUTHORED CONTENT -->
 <p id="classSummary">
 Use the <code>chrome.proxy</code> module to manage Chrome's
 proxy settings. This module relies on the <a href="preferences.html">preferences
   API</a> for getting and setting the proxy configuration.
 </p>
 
 <h2 id="manifest">Manifest</h2>
@@ skipping 159 matching lines @@
     },
     bypassList: ["foobar.com"]
   }
 };
 chrome.proxy.settings.set(
     {value: config, scope: 'regular'},
     function() {});
 </pre>
 
 <p>
-The following code sets a custom PAC script.
+The following code sets a custom pac script.
 </p>
 
 <pre>
 var config = {
   mode: "pac_script",
   pacScript: {
     data: "function FindProxyForURL(url, host) {\n" +
           "  if (host == 'foobar.com')\n" +
           "    return 'PROXY blackhole:80';\n" +
           "  return 'DIRECT';\n" +
           "}"
   }
 };
 chrome.proxy.settings.set(
     {value: config, scope: 'regular'},
     function() {});
 </pre>
 
 <p>
 The next snippet queries the currently effective proxy settings. The effective
-proxy settings can be determined by another extension or by a policy. See the <a
-  href="preferences.html">Preferences API</a> documentation for details.
+proxy settings can be determined by another extension or by a policy, see the <a
+  href="preferences.html">Preferences API</a> documentation.
 </p>
 
 <pre>
 chrome.proxy.settings.getEffective(
     {'incognito': false},
     function(config) {console.log(JSON.stringify(config));});
 </pre>
 
 <p>
 Note that the <code>value</code> object passed to <code>set()</code> is not
 identical to the <code>value</code> object passed to callback function of
 <code>getEffective()</code>. The latter will contain a
 <code>rules.httpProxy.port</code> element.
 </p>
 
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