KSV: Fix a11y spoken for shortcut item

Currently spoken of shortcut viewer shortcut item is verbose and has
not seperation between description and shortcut.

This patch fixes the two a11y spoken issues by:
1. Remove category text in each item.
2. Add a punctuation between description and shortcut.

Bug: 876398, 876400
Test: manual.
Change-Id: I42b1558c0e165ad7a25227475309c205b6fdabaa
Reviewed-on: https://chromium-review.googlesource.com/1244158Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Commit-Queue: Tao Wu <wutao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594151}

ash/components/shortcut_viewer/views/keyboard_shortcut_item_view.cc

@@ -137,9 +137,8 @@ KeyboardShortcutItemView::KeyboardShortcutItemView(
   // redundant child label text is not also spoken.
   GetViewAccessibility().OverrideRole(ax::mojom::Role::kListItem);
   GetViewAccessibility().OverrideIsLeaf();
-  accessible_name_ = GetStringForCategory(category_) +
-                     description_label_view_->text() +
-                     shortcut_label_view_->text();
+  accessible_name_ = description_label_view_->text() +
+                     base::ASCIIToUTF16(", ") + shortcut_label_view_->text();
 }
 
 void KeyboardShortcutItemView::GetAccessibleNodeData(