[DevTools] Show icon in top toolbar when Node target is available

third_party/WebKit/Source/devtools/front_end/main/nodeIcon.css

Index: third_party/WebKit/Source/devtools/front_end/main/nodeIcon.css
diff --git a/third_party/WebKit/Source/devtools/front_end/main/nodeIcon.css b/third_party/WebKit/Source/devtools/front_end/main/nodeIcon.css
new file mode 100644
index 0000000000000000000000000000000000000000..326247d333a78ab08fd73ca13f81f8e17c86c731
--- /dev/null
+++ b/third_party/WebKit/Source/devtools/front_end/main/nodeIcon.css
@@ -0,0 +1,23 @@
+/*
+ * Copyright 2017 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.
+ */
+
+.node-icon {
+    width: 28px;
+    height: 26px;
+    background-image: url(Images/nodeIcon.png);
+    background-size: 17px 17px;
+    background-repeat: no-repeat;
+    background-position: center;
+    opacity: 0.8;
+}
+
+.node-icon:hover {
+    opacity: 1.0;
+}
+
+.node-icon.inactive {
+    filter: grayscale(100%);
+}