Add a minimal Security panel to DevTools (behind a hidden experiment).

Source/devtools/front_end/security/securityPanel.css

+/* Copyright (c) 2015 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.
+ */
+
+.security.panel {
+  margin: 1em;
+}
+
+.security.panel .lock-icon, .security.panel .security-state {
+  display: inline-block;
+  margin: 0.2em;
+  vertical-align: middle;
+}
+
+.security.panel .lock-icon {
+    width: 16px;
+    height: 16px;
+    border-radius: 2px;
+    background-image: url(Images/securityStateHttp.png);
+    background-size: cover;
+}
+.security.panel .lock-icon.unknown  {background-image: url(Images/securityStateHttp.png);}
+.security.panel .lock-icon.http     {background-image: url(Images/securityStateHttp.png);}
+.security.panel .lock-icon.insecure {background-image: url(Images/securityStateInsecure.png);}
+.security.panel .lock-icon.warning  {background-image: url(Images/securityStateWarning.png);}
+.security.panel .lock-icon.secure   {background-image: url(Images/securityStateSecure.png);}
+
+@media (-webkit-min-device-pixel-ratio: 1.5) {
+  .security.panel .lock-icon.unknown  {background-image: url(Images/securityStateHttp_2x.png);}
+  .security.panel .lock-icon.http     {background-image: url(Images/securityStateHttp_2x.png);}
+  .security.panel .lock-icon.insecure {background-image: url(Images/securityStateInsecure_2x.png);}
+  .security.panel .lock-icon.warning  {background-image: url(Images/securityStateWarning_2x.png);}
+  .security.panel .lock-icon.secure   {background-image: url(Images/securityStateSecure_2x.png);}
+}