Add sample extension that allows setting plugin-specific content settings.

chrome/common/extensions/docs/examples/extensions/plugin_settings/domui/css/select.css

Index: chrome/common/extensions/docs/examples/extensions/plugin_settings/domui/css/select.css
diff --git a/chrome/common/extensions/docs/examples/extensions/plugin_settings/domui/css/select.css b/chrome/common/extensions/docs/examples/extensions/plugin_settings/domui/css/select.css
new file mode 100644
index 0000000000000000000000000000000000000000..ba951e58ab062401b19f74ddf20e76bf964e0cd7
--- /dev/null
+++ b/chrome/common/extensions/docs/examples/extensions/plugin_settings/domui/css/select.css
@@ -0,0 +1,51 @@
+/* Copyright (c) 2011 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.
+ *
+ * This is the generic select css used on various WebUI implementations.
+ */
+
+select {
+  -webkit-appearance: button;
+  -webkit-border-radius: 2px;
+  -webkit-box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
+  -webkit-padding-end: 20px;
+  -webkit-padding-start: 2px;
+  -webkit-user-select: none;
+  background-image: url("../images/select.png"),
+                    -webkit-linear-gradient(#fafafa, #f4f4f4 40%, #e5e5e5);
+  background-position: center right;
+  background-repeat: no-repeat;
+  border: 1px solid #aaa;
+  color: #555;
+  font-size: inherit;
+  margin: 0;
+  overflow: hidden;
+  padding-top: 2px;
+  padding-bottom: 2px;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+html[dir='rtl'] select {
+  background-position: center left;
+}
+
+
+select:disabled {
+  color: graytext;
+}
+
+select:enabled:hover {
+  -webkit-box-shadow: 0 1px 3px rgba(0, 0, 0, 0.2);
+  background-image: url("../images/select.png"),
+                    -webkit-linear-gradient(#fefefe, #f8f8f8 40%, #e9e9e9);
+  color: #333;
+}
+
+select:enabled:active {
+  -webkit-box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.2);
+  background-image: url("../images/select.png"),
+                    -webkit-linear-gradient(#f4f4f4, #efefef 40%, #dcdcdc);
+  color: #444;
+}