MD Downloads: limit the amount of downloads we send

chrome/browser/resources/md_downloads/crisper.js

 // Copyright 2015 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.
 
 if (typeof Polymer == 'undefined')
   Polymer = {dom: 'shadow'};
 else
   console.error('Polymer is already defined.');
 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
@@ skipping 1560 matching lines @@
     download: function(url) {
       var a = document.createElement('a');
       a.href = url;
       a.setAttribute('download', '');
       a.click();
     },
 
     /** @param {string} id ID of the download that the user started dragging. */
     drag: chromeSendWithId('drag'),
 
-    /** @private {boolean} */
-    isSearching_: false,
+    /** Loads more downloads with the current search terms. */
+    loadMore: function() {
+      chrome.send('getDownloads', this.searchTerms_);
+    },
 
     /**
      * @return {boolean} Whether the user is currently searching for downloads
      *     (i.e. has a non-empty search term).
      */
     isSearching: function() {
-      return this.isSearching_;
+      return this.searchTerms_.length > 0;
     },
 
     /** Opens the current local destination for downloads. */
     openDownloadsFolder: chrome.send.bind(chrome, 'openDownloadsFolder'),
 
     /**
      * @param {string} id ID of the download to run locally on the user's box.
      */
     openFile: chromeSendWithId('openFile'),
 
@@ skipping 11 matching lines @@
      *     warnings.
      */
     saveDangerous: chromeSendWithId('saveDangerous'),
 
     /** @param {string} searchText What to search for. */
     search: function(searchText) {
       if (this.searchText_ == searchText)
         return;
 
       this.searchText_ = searchText;
+      this.searchTerms_ = ActionService.splitTerms(this.searchText_);
+      this.loadMore();
+    },
 
-      var terms = ActionService.splitTerms(searchText);
-      this.isSearching_ = terms.length > 0;
+    /** @private {Array<string>} */
+    searchTerms_: [],
 
-      chrome.send('getDownloads', terms);
-    },
+    /** @private {string} */
+    searchText_: '',
 
     /**
      * Shows the local folder a finished download resides in.
      * @param {string} id ID of the download to show.
      */
     show: chromeSendWithId('show'),
 
     /** Undo download removal. */
     undo: chrome.send.bind(chrome, 'undo'),
   };
@@ skipping 15332 matching lines @@
       items_: {
         type: Array,
         value: function() { return []; },
       },
     },
 
     hostAttributes: {
       loading: true,
     },
 
+    listeners: {
+      'downloads-list.scroll': 'onListScroll_',
+    },
+
     observers: [
       'itemsChanged_(items_.*)',
     ],
 
     /** @private */
     clearAll_: function() {
       this.set('items_', []);
     },
 
     /** @private */
@@ skipping 47 matching lines @@
      * @param {Event} e
      * @private
      */
     onCommand_: function(e) {
       if (e.command.id == 'clear-all-command')
         downloads.ActionService.getInstance().clearAll();
       else if (e.command.id == 'undo-command')
         downloads.ActionService.getInstance().undo();
     },
 
+    /**
+     * @param {Event} e
+     * @private
+     */
+    onListScroll_: function(e) {
+      var list = this.$['downloads-list'];
+      if (list.scrollHeight > list.offsetHeight &&
+          list.scrollTop + list.offsetHeight == list.scrollHeight) {
+        // Reached the end of the scrollback. Attempt to load more items.
+        downloads.ActionService.getInstance().loadMore();
+      }
+    },
+
     /** @private */
     onLoad_: function() {
       cr.ui.decorate('command', cr.ui.Command);
       document.addEventListener('canExecute', this.onCanExecute_.bind(this));
       document.addEventListener('command', this.onCommand_.bind(this));
 
-      // Shows all downloads.
-      downloads.ActionService.getInstance().search('');
+      downloads.ActionService.getInstance().loadMore();
     },
 
     /**
      * @param {number} index
      * @private
      */
     removeItem_: function(index) {
       this.splice('items_', index, 1);
       this.updateHideDates_(index, index);
     },
@@ skipping 51 matching lines @@
     Manager.get().updateItem_(index, data);
   };
 
   return {Manager: Manager};
 });
 // Copyright 2015 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.
 
 window.addEventListener('load', downloads.Manager.onLoad);