Revert of MD Downloads: track downloads in C++, dispatch discrete JS updates

chrome/browser/resources/md_downloads/crisper.js

Index: chrome/browser/resources/md_downloads/crisper.js
diff --git a/chrome/browser/resources/md_downloads/crisper.js b/chrome/browser/resources/md_downloads/crisper.js
index 3b32922d2d9a9d6b8a4f0cadd1246e8961f651f1..da4452387f9851bc529b874c8665cd0736bb3498 100644
--- a/chrome/browser/resources/md_downloads/crisper.js
+++ b/chrome/browser/resources/md_downloads/crisper.js
@@ -1531,27 +1531,6 @@
   /** @constructor */
   function ActionService() {}
 
-  /**
-   * @param {string} searchText Input typed by the user into a search box.
-   * @return {Array<string>} A list of terms extracted from |searchText|.
-   */
-  ActionService.splitTerms = function(searchText) {
-    /**
-     * @param {string} s
-     * @return {string} |s| without whitespace at the beginning or end.
-     */
-    function trim(s) { return s.trim(); }
-
-    /**
-     * @param {string} s
-     * @return {boolean} Whether |s| is empty.
-     */
-    function notEmpty(s) { return s.length > 0; }
-
-    // Split quoted terms (e.g., 'The "lazy" dog' => ['The', 'lazy', 'dog']).
-    return searchText.split(/"([^"]*)"/).map(trim).filter(notEmpty);
-  };
-
   ActionService.prototype = {
     /** @param {string} id ID of the download to cancel. */
     cancel: chromeSendWithId('cancel'),
@@ -1583,7 +1562,7 @@
      *     (i.e. has a non-empty search term).
      */
     isSearching: function() {
-      return !!this.searchText_;
+      return this.searchText_.length > 0;
     },
 
     /** Opens the current local destination for downloads. */
@@ -1615,7 +1594,10 @@
         return;
 
       this.searchText_ = searchText;
-      chrome.send('getDownloads', ActionService.splitTerms(searchText));
+
+      // Split quoted terms (e.g., 'The "lazy" dog' => ['The', 'lazy', 'dog']).
+      function trim(s) { return s.trim(); }
+      chrome.send('getDownloads', searchText.split(/"([^"]*)"/).map(trim));
     },
 
     /**
@@ -16955,58 +16937,17 @@
 
     properties: {
       hasDownloads_: {
-        observer: 'hasDownloadsChanged_',
         type: Boolean,
+        value: false,
       },
 
       items_: {
         type: Array,
-        value: function() { return []; },
       },
     },
 
     hostAttributes: {
       loading: true,
-    },
-
-    observers: [
-      'itemsChanged_(items_.*)',
-    ],
-
-    /** @private */
-    clearAll_: function() {
-      this.set('items_', []);
-    },
-
-    /** @private */
-    hasDownloadsChanged_: function() {
-      if (loadTimeData.getBoolean('allowDeletingHistory'))
-        this.$.toolbar.downloadsShowing = this.hasDownloads_;
-
-      if (this.hasDownloads_) {
-        this.$['downloads-list'].fire('iron-resize');
-      } else {
-        var isSearching = downloads.ActionService.getInstance().isSearching();
-        var messageToShow = isSearching ? 'noSearchResults' : 'noDownloads';
-        this.$['no-downloads'].querySelector('span').textContent =
-            loadTimeData.getString(messageToShow);
-      }
-    },
-
-    /**
-     * @param {number} index
-     * @param {!Array<!downloads.Data>} list
-     * @private
-     */
-    insertItems_: function(index, list) {
-      this.splice.apply(this, ['items_', index, 0].concat(list));
-      this.updateHideDates_(index, index + list.length);
-      this.removeAttribute('loading');
-    },
-
-    /** @private */
-    itemsChanged_: function() {
-      this.hasDownloads_ = this.items_.length > 0;
     },
 
     /**
@@ -17047,64 +16988,78 @@
     },
 
     /**
-     * @param {number} index
+     * @return {number} The number of downloads shown on the page.
      * @private
      */
-    removeItem_: function(index) {
-      this.splice('items_', index, 1);
-      this.updateHideDates_(index, index);
-    },
-
-    /**
-     * @param {number} start
-     * @param {number} end
+    size_: function() {
+      return this.items_.length;
+    },
+
+    /**
+     * Called when all items need to be updated.
+     * @param {!Array<!downloads.Data>} list A list of new download data.
      * @private
      */
-    updateHideDates_: function(start, end) {
-      for (var i = start; i <= end; ++i) {
-        var current = this.items_[i];
-        if (!current)
-          continue;
-        var prev = this.items_[i - 1];
-        current.hideDate = !!prev && prev.date_string == current.date_string;
-      }
-    },
-
-    /**
-     * @param {number} index
+    updateAll_: function(list) {
+      /** @private {!Object<number>} */
+      this.idToIndex_ = {};
+
+      for (var i = 0; i < list.length; ++i) {
+        var data = list[i];
+
+        this.idToIndex_[data.id] = data.index = i;
+
+        var prev = list[i - 1];
+        data.hideDate = !!prev && prev.date_string == data.date_string;
+      }
+
+      // TODO(dbeam): this resets the scroll position, which is a huge bummer.
+      // Removing something from the bottom of the list should not scroll you
+      // back to the top. The grand plan is to restructure how the C++ sends the
+      // JS data so that it only gets updates (rather than the most recent set
+      // of items). TL;DR - we can't ship with this bug.
+      this.items_ = list;
+
+      var hasDownloads = this.size_() > 0;
+      if (!hasDownloads) {
+        var isSearching = downloads.ActionService.getInstance().isSearching();
+        var messageToShow = isSearching ? 'noSearchResults' : 'noDownloads';
+        this.$['no-downloads'].querySelector('span').textContent =
+            loadTimeData.getString(messageToShow);
+      }
+      this.hasDownloads_ = hasDownloads;
+
+      if (loadTimeData.getBoolean('allowDeletingHistory'))
+        this.$.toolbar.downloadsShowing = this.hasDownloads_;
+
+      this.removeAttribute('loading');
+    },
+
+    /**
      * @param {!downloads.Data} data
      * @private
      */
-    updateItem_: function(index, data) {
+    updateItem_: function(data) {
+      var index = this.idToIndex_[data.id];
       this.set('items_.' + index, data);
-      this.updateHideDates_(index, index);
       this.$['downloads-list'].updateSizeForItem(index);
     },
   });
 
-  Manager.clearAll = function() {
-    Manager.get().clearAll_();
+  Manager.size = function() {
+    return document.querySelector('downloads-manager').size_();
   };
 
-  /** @return {!downloads.Manager} */
-  Manager.get = function() {
-    return queryRequiredElement('downloads-manager');
+  Manager.updateAll = function(list) {
+    document.querySelector('downloads-manager').updateAll_(list);
   };
 
-  Manager.insertItems = function(index, list) {
-    Manager.get().insertItems_(index, list);
+  Manager.updateItem = function(item) {
+    document.querySelector('downloads-manager').updateItem_(item);
   };
 
   Manager.onLoad = function() {
-    Manager.get().onLoad_();
-  };
-
-  Manager.removeItem = function(index) {
-    Manager.get().removeItem_(index);
-  };
-
-  Manager.updateItem = function(index, data) {
-    Manager.get().updateItem_(index, data);
+    document.querySelector('downloads-manager').onLoad_();
   };
 
   return {Manager: Manager};