DevTools: Introduce Landing page for Timeline panel.

third_party/WebKit/Source/devtools/front_end/timeline/timelineLandingPage.css

+/*
+ * Copyright (c) 2016 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.
+ */
+
+.timeline-landing-page {
+    align-self: center;
+    max-width: 500px;
+}
+
+.timeline-landing-page .tabbed-pane {
+    padding: 10px 0 0 0;
+}
+
+.timeline-landing-page .tabbed-pane-header {
+    background-color: inherit;
+    flex-basis: 33px;
+    align-items: center;
+}
+
+.timeline-landing-page .tabbed-pane-header-contents {
+    margin-left: 0;
+}
+
+.timeline-landing-page .tabbed-pane-header-tab {
+    border: none;
+    padding: 4px 12px;
+    cursor: pointer;
+    font-size: 13px;
+    height: 30px;
+}
+
+.timeline-landing-page .timeline-perspective-body {
+    align-items: stretch;
+    line-height: 1.5;
+    padding: 12px;
+    white-space: pre-line;
+    width: 100%;
+}
+
+.timeline-landing-page .timeline-perspective-body > div {
+    margin-bottom: 12px;
+    flex-shrink: 0;
+}
+
+.timeline-landing-page button.action-button {
+    width: 90px;
+    height: 26px;
+    margin: 10px 0 0 0;
+}
+
+.timeline-landing-page .recording-setting {
+    display: flex;
+    align-items: flex-start;
+    margin-bottom: 2px !important;
+}
+
+.timeline-landing-page .recording-setting input {
+    margin-left: 0;
+    margin-right: 8px;
+}
+
+.timeline-landing-page .recording-setting label {
+    flex: 100px 0 0;
+}
+
+.timeline-landing-page .recording-setting-description {
+    color: #999;
+}