[NTP Snippets] Persist snippets in a LevelDB instead of prefs

chrome/browser/resources/snippets_internals.js

 // Copyright 2016 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.
 
 cr.define('chrome.SnippetsInternals', function() {
   'use strict';
 
+  // Stores the list of snippets we received in receiveSnippets.
+  var lastSnippets = [];
+
   function initialize() {
     $('submit-download').addEventListener('click', function(event) {
       chrome.send('download', [$('hosts-input').value]);
       event.preventDefault();
     });
 
     $('submit-clear').addEventListener('click', function(event) {
       chrome.send('clear');
       event.preventDefault();
     });
 
     $('submit-dump').addEventListener('click', function(event) {
-      chrome.send('dump');
+      downloadJson(JSON.stringify(lastSnippets));
       event.preventDefault();
     });
 
     $('last-json-button').addEventListener('click', function(event) {
       $('last-json-container').classList.toggle('hidden');
     });
 
     $('last-json-dump').addEventListener('click', function(event) {
-      receiveJsonToDownload($('last-json-text').innerText);
+      downloadJson($('last-json-text').innerText);
       event.preventDefault();
     });
 
     $('discarded-snippets-clear').addEventListener('click', function(event) {
       chrome.send('clearDiscarded');
       event.preventDefault();
     });
 
     chrome.send('loaded');
   }
@@ skipping 10 matching lines @@
   }
 
   function receiveHosts(hosts) {
     displayList(hosts, 'hosts');
 
     $('hosts-input').value = hosts.list.map(
       function(host) { return host.url;}).join(' ');
   }
 
   function receiveSnippets(snippets) {
+    lastSnippets = snippets;
     displayList(snippets, 'snippets', 'snippet-title');
   }
 
   function receiveDiscardedSnippets(discardedSnippets) {
     displayList(discardedSnippets, 'discarded-snippets',
                 'discarded-snippet-title');
   }
 
   function receiveJson(json) {
     var trimmed = json.trim();
     var hasContent = (trimmed && trimmed != '{}');
 
     if (hasContent) {
       receiveProperty('last-json-text', trimmed);
       $('last-json').classList.remove('hidden');
     } else {
       $('last-json').classList.add('hidden');
     }
   }
 
-  function receiveJsonToDownload(json) {
+  function downloadJson(json) {
     // Redirect the browser to download data in |json| as a file "snippets.json"
     // (Setting Content-Disposition: attachment via a data: URL is not possible;
     // create a link with download attribute and simulate a click, instead.)
     var link = document.createElement('a');
     link.download = 'snippets.json';
     link.href = 'data:,' + json;
     link.click();
   }
 
   function displayList(object, domId, titleClass) {
@@ skipping 24 matching lines @@
 
   // Return an object with all of the exports.
   return {
     initialize: initialize,
     setHostRestricted: setHostRestricted,
     receiveProperty: receiveProperty,
     receiveHosts: receiveHosts,
     receiveSnippets: receiveSnippets,
     receiveDiscardedSnippets: receiveDiscardedSnippets,
     receiveJson: receiveJson,
-    receiveJsonToDownload: receiveJsonToDownload,
   };
 });
 
 document.addEventListener('DOMContentLoaded',
                           chrome.SnippetsInternals.initialize);