DevTools: [Documentation] Update empty page style

Source/devtools/front_end/documentationView.css

 /*
  * Copyright 2014 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.
  */
 
 .documentation-code {
     border: 1px solid gray;
     border-radius: 6px;
     padding: 10px;
@@ skipping 76 matching lines @@
 
 .documentation-box {
     padding: 6px;
     padding-left: 10px;
     padding-right: 10px;
     text-decoration: none;
     margin-left: 10px;
     margin-top: 5px;
     border-radius: 5px;
 }
+
+.documentation-not-found {
+    display: flex;

[loislo, 2014/09/10 06:18:15]

do we actually need this property on the title.

+    justify-content: center;
+    align-items: flex-end;

[loislo, 2014/09/10 06:18:15]

I'm not sure that we need this property. Could you please clarify why we need
it.

[semeny, 2014/09/10 09:04:59]

We need to use flex and other flex properties to align text just in center of
the tab.

+    font-size: 24px;
+    font-weight: bold;
+    color: rgb(191, 191, 191);
+    flex-shrink: 0;
+    flex-grow: 2;
+}
+
+.documentation-empty-page {
+    display: flex;
+    flex-direction: column !important;
+}
+
+.documentation-empty-page-align {
+    flex-grow: 3;
+}