Disable modifying extensions when in managed mode.

chrome/browser/resources/uber/uber_shared.css

Index: chrome/browser/resources/uber/uber_shared.css
===================================================================
--- chrome/browser/resources/uber/uber_shared.css	(revision 142678)
+++ chrome/browser/resources/uber/uber_shared.css	(working copy)
@@ -116,3 +116,48 @@
 body.uber-frame section > div:only-of-type {
   -webkit-box-flex: 1;
 }
+
+/* Styles for a hideable notification banner at the top of a page.
+ * See the Options page .managed-prefs-banner for a usage example. */
+.page.showing-banner {
+  margin-top: 45px;
+}
+
+.page-banner {
+  background-color: white;
+  width: 100%;
+  z-index: 2;
+}
+
+.page:not(.showing-banner) .page-banner {
+  display: none;
+}
+
+.page-banner-gradient {
+  background: -webkit-linear-gradient(rgb(255, 242, 183),
+                                      rgb(250, 230, 145));
+  border: 1px solid rgb(201, 189, 141);
+  border-radius: 3px;
+  height: 25px;
+  margin: 9px 9px 0 9px;
+}
+
+.page-banner .page-banner-gradient {
+  -webkit-margin-end: 20px;
+  -webkit-margin-start: 0;
+  margin-bottom: 9px;
+}
+
+.page-banner-text {
+  background-image: url('chrome://theme/IDR_MANAGED');
+  background-position: 5px center;
+  background-repeat: no-repeat;
+  display: block;
+  line-height: 24px;
+  padding-left: 26px;
+}
+
+.page-banner.clickable:active .page-banner-text {
+  background: -webkit-linear-gradient(rgb(250, 230, 145),
+                                      rgb(255, 242, 183));
+}