Revert CL 117933003. Re-add resource speculative prefetching code.

chrome/browser/resources/predictors/resource_prefetch_predictor.js

+// 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.
+
+/**
+ * Requests the database from the backend.
+ */
+function requestResourcePrefetchPredictorDb() {
+  chrome.send('requestResourcePrefetchPredictorDb');
+}
+
+/**
+ * Callback from backend with the database contents. Sets up some globals and
+ * calls to create the UI.
+ * @param {Dictionary} database Information about ResourcePrefetchPredictor
+ *     including the database as a flattened list, a boolean indicating if the
+ *     system is enabled.
+ */
+function updateResourcePrefetchPredictorDb(database) {
+  updateResourcePrefetchPredictorDbView(database);
+}
+
+/**
+ * Truncates the string to keep the database readable.
+ * @param {string} str The string to truncate.
+ * @return {string} The truncated string.
+ */
+function truncateString(str) {
+  return str.length < 100 ? str : str.substring(0, 99);
+}
+
+/**
+ * Updates the table from the database.
+ * @param {Dictionary} database Information about ResourcePrefetchPredictor
+ *     including the database as a flattened list, a boolean indicating if the
+ *     system is enabled and the current hit weight.
+ */
+function updateResourcePrefetchPredictorDbView(database) {
+  if (!database.enabled) {
+    $('rpp_enabled').style.display = 'none';
+    $('rpp_disabled').style.display = 'block';
+    return;
+  } else {
+    $('rpp_enabled').style.display = 'block';
+    $('rpp_disabled').style.display = 'none';
+  }
+
+  var hasUrlData = database.url_db && database.url_db.length > 0;
+  var hasHostData = database.host_db && database.host_db.length > 0;
+
+  if (hasUrlData)
+    renderCacheData($('rpp_url_body'), database.url_db);
+  if (hasHostData)
+    renderCacheData($('rpp_host_body'), database.host_db);
+}
+
+/**
+ * Renders cache data for URL or host based data.
+ * @param {HTMLElement} body element of table to render into.
+ * @param {Dictionary} database to render.
+ */
+function renderCacheData(body, database) {
+  body.textContent = '';
+  for (var i = 0; i < database.length; ++i) {
+    var main = database[i];
+
+    for (var j = 0; j < main.resources.length; ++j) {
+      var resource = main.resources[j];
+      var row = document.createElement('tr');
+
+      if (j == 0) {
+        var t = document.createElement('td');
+        t.rowSpan = main.resources.length;
+        t.textContent = truncateString(main.main_frame_url);
+        t.className = 'last';
+        row.appendChild(t);
+      }
+
+      if (j == main.resources.length - 1)
+        row.className = 'last';
+
+      row.appendChild(document.createElement('td')).textContent =
+          truncateString(resource.resource_url);
+      row.appendChild(document.createElement('td')).textContent =
+          resource.resource_type;
+      row.appendChild(document.createElement('td')).textContent =
+          resource.number_of_hits;
+      row.appendChild(document.createElement('td')).textContent =
+          resource.number_of_misses;
+      row.appendChild(document.createElement('td')).textContent =
+          resource.consecutive_misses;
+      row.appendChild(document.createElement('td')).textContent =
+          resource.position;
+      row.appendChild(document.createElement('td')).textContent =
+          resource.score;
+      body.appendChild(row);
+    }
+  }
+}
+
+document.addEventListener('DOMContentLoaded',
+                          requestResourcePrefetchPredictorDb);