[DevTools] Introduce a sidebar with a drop-down

third_party/WebKit/Source/devtools/front_end/resources/frameMenuSidebar.css

Index: third_party/WebKit/Source/devtools/front_end/resources/frameMenuSidebar.css
diff --git a/third_party/WebKit/Source/devtools/front_end/resources/frameMenuSidebar.css b/third_party/WebKit/Source/devtools/front_end/resources/frameMenuSidebar.css
new file mode 100644
index 0000000000000000000000000000000000000000..2f9700f8d41a834c62ec8eaa0f8b28f8b190be98
--- /dev/null
+++ b/third_party/WebKit/Source/devtools/front_end/resources/frameMenuSidebar.css
@@ -0,0 +1,33 @@
+/*
+ * 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.
+ */
+
+
+.frame-selector {
+    border-width: 0;
+    display: flex;
+    align-items: center;
+    background: inherit;
+    padding: 6px 6px 6px 2px;
+    border-width: 1px;
+    border-color: transparent;
+    border-style: solid;
+}
+
+.frame-selector:hover {
+    border-color: lightgray;
+}
+
+.frame-selector:focus {
+    border-color: lightgray;
+}
+
+.frame-name {
+    flex-grow: 1;
+    text-align: start;
+    overflow: hidden;
+    white-space: nowrap;
+    margin: 0 4px 0 2px;
+}