Updating the samples page to reflect the examples that have been retired.

src/site/samples/searchable_list/index.markdown

----
-layout: default
-title: Searchable List
-live_example_url: example/index.html
-
-header:
-  css: ["/samples/samples.css"]
----
-
-## {{ page.title }}
-
-This simple application shows the use of a custom element where list data is
-searchable. The demonstrates the following parts of Polymer:
-
-* defining custom elements
-* the `<template>` tag
-* HTML imports
-* data binding
-
-
-The `<searchable-list>` element uses data binding to implement search.
-See the `searchable_list.html` and the `searchable_list.dart` files for the
-code.
-
-The `SearchableList` class uses three variables in the search implementation:
-
-* `data` stores all the data in the list
-* `searchParam` stores the search parameter
-* `results` stores the elements of `data` that match the search paramater
-
-When the user types in the search input, the `search()` method triggers, and
-the value of `results` is updated.  Since `results` is an observable variable,
-its representation in the UI automatically updates as its contents change.
-
-Here is the minimal code for required to implement search
-(`searchable_list.dart`):
-
-    search() {
-      results.clear();
-      String lower = searchParam.toLowerCase();
-      results.addAll(data.where((d) => d.toLowerCase().contains(lower)));
-    }
-
-Any changes to `searchParam` trigger  `search()`. Here is the code for that
-(the `enteredView()` method in `searchable_list.dart`):
-
-    onPropertyChange(this, #searchParam, search);
-
-Read the
-[source](https://github.com/dart-lang/sample-searchable-list).
-
-<iframe class="running-app-frame"
-        style="height:500px;width:100%;"
-        src="{{page.live_example_url}}">
-</iframe>
-
-See all [samples](/samples/)