downloads: break downloads.js into more classes/files.

chrome/browser/resources/downloads/focus_row.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.
+
+cr.define('downloads', function() {
+  /**
+   * Provides an implementation for a single column grid.
+   * @constructor
+   * @extends {cr.ui.FocusRow}
+   */
+  function FocusRow() {}
+
+  /**
+   * Decorates |focusRow| so that it can be treated as a FocusRow.
+   * @param {Element} focusRow The element that has all the columns represented
+   *     by |itemView|.
+   * @param {!downloads.ItemView} itemView The item view this row cares about.
+   * @param {Node} boundary Focus events are ignored outside of this node.
+   */
+  FocusRow.decorate = function(focusRow, itemView, boundary) {
+    focusRow.__proto__ = FocusRow.prototype;
+    focusRow.decorate(boundary);
+
+    // Add all clickable elements as a row into the grid.
+    focusRow.addElementIfFocusable_(itemView.fileLink, 'name');
+    focusRow.addElementIfFocusable_(itemView.srcUrl, 'url');
+    focusRow.addElementIfFocusable_(itemView.show, 'show');
+    focusRow.addElementIfFocusable_(itemView.retry, 'retry');
+    focusRow.addElementIfFocusable_(itemView.pause, 'pause');
+    focusRow.addElementIfFocusable_(itemView.resume, 'resume');
+    focusRow.addElementIfFocusable_(itemView.safeRemove, 'remove');
+    focusRow.addElementIfFocusable_(itemView.cancel, 'cancel');
+    focusRow.addElementIfFocusable_(itemView.restore, 'save');
+    focusRow.addElementIfFocusable_(itemView.save, 'save');
+    focusRow.addElementIfFocusable_(itemView.dangerRemove, 'discard');
+    focusRow.addElementIfFocusable_(itemView.discard, 'discard');
+    focusRow.addElementIfFocusable_(itemView.controlledBy, 'extension');
+  };
+
+  FocusRow.prototype = {
+    __proto__: cr.ui.FocusRow.prototype,
+
+    /** @override */
+    getEquivalentElement: function(element) {
+      if (this.focusableElements.indexOf(element) > -1)
+        return assert(element);
+
+      // All elements default to another element with the same type.
+      var columnType = element.getAttribute('column-type');
+      var equivalent = this.querySelector('[column-type=' + columnType + ']');
+
+      if (this.focusableElements.indexOf(equivalent) < 0) {
+        var equivalentTypes =
+            ['show', 'retry', 'pause', 'resume', 'remove', 'cancel'];
+        if (equivalentTypes.indexOf(columnType) != -1) {
+          var allTypes = equivalentTypes.map(function(type) {
+            return '[column-type=' + type + ']:not([hidden])';
+          }).join(', ');
+          equivalent = this.querySelector(allTypes);
+        }
+      }
+
+      // Return the first focusable element if no equivalent element is found.
+      return assert(equivalent || this.focusableElements[0]);
+    },
+
+    /**
+     * @param {Element} element The element that should be added.
+     * @param {string} type The column type to use for the element.
+     * @private
+     */
+    addElementIfFocusable_: function(element, type) {
+      if (this.shouldFocus_(element)) {
+        this.addFocusableElement(element);
+        element.setAttribute('column-type', type);

[asanka, 2015/03/10 04:15:51]

Rather than using [column-type], can we code the column type into the template?

[Dan Beam, 2015/03/10 05:41:02]

i copied the code from here:
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/res...

i understand we don't always get a chance to change code that's already in
place, so this is a good time to re-evaluate.  but a) hcarmona@ is more familiar
with this code, and b) I'd really like to do this separately if possible -- this
CL is a pain for you to review because it's large and complex [enough already].

[asanka, 2015/03/11 19:57:49]

SG.

+      }
+    },
+
+    /**
+     * Determines if element should be focusable.
+     * @param {Element} element
+     * @return {boolean}
+     * @private
+     */
+    shouldFocus_: function(element) {

[asanka, 2015/03/10 04:15:50]

Doesn't cr.ui.FocusRow deal with visibility?

[Dan Beam, 2015/03/10 05:41:02]

no,
https://code.google.com/p/chromium/codesearch#chromium/src/ui/webui/resources...

+      if (!element)
+        return false;
+
+      // Hidden elements are not focusable.
+      var style = window.getComputedStyle(element);
+      if (style.visibility == 'hidden' || style.display == 'none')
+        return false;
+
+      // Verify all ancestors are focusable.
+      return !element.parentElement || this.shouldFocus_(element.parentElement);
+    },
+  };
+
+  return {FocusRow: FocusRow};
+});