Implemented new channel switcher UI.

chrome/browser/resources/help/channel_change_page.css

Index: chrome/browser/resources/help/channel_change_page.css
diff --git a/chrome/browser/resources/help/channel_change_page.css b/chrome/browser/resources/help/channel_change_page.css
new file mode 100644
index 0000000000000000000000000000000000000000..50135e430bcdbcfaef135f5bd9fff7ffa25aaaa0
--- /dev/null
+++ b/chrome/browser/resources/help/channel_change_page.css
@@ -0,0 +1,43 @@
+/* Copyright (c) 2013 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.
+ */
+
+#channel-change-page {
+  min-height: 200px;
+  padding: 20px 25px;
+  width: 500px;
+}
+
+.channel-change-page-title {

[Nikita (slow), 2013/06/21 12:21:33]

nit: "Do not create a class for only one element; use the element ID instead."
http://dev.chromium.org/developers/web-development-style-guide

[ygorshenin1, 2013/06/21 17:24:58]

Done.

+  margin-bottom: 30px;
+}
+
+.channel-change-page-channel label {
+  margin-left: 10px;
+}
+
+.channel-change-page-message-title {
+  margin-bottom: 25px;
+}
+
+.channel-change-page-channel {
+  display: block;
+  margin: 15px 25px;
+}
+
+.show-when-selected-channel-requires-powerwash,
+.show-when-selected-channel-requires-delayed-update,
+.show-when-selected-channel-good,
+.show-when-selected-channel-unstable {
+  display: none !important;
+}
+
+.selected-channel-requires-powerwash
+.show-when-selected-channel-requires-powerwash,
+.selected-channel-requires-delayed-update
+.show-when-selected-channel-requires-delayed-update,
+.selected-channel-good .show-when-selected-channel-good,
+.selected-channel-unstable .show-when-selected-channel-unstable {
+  display: block !important;
+}