Added introductory tables to Chrome apps APIs.

chrome/common/extensions/docs/static/css/site.css

 /* Copyright (c) 2012 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.
  */
 
 .hidden {
   display: none;
 }
 
 body {
@@ skipping 295 matching lines @@
 #gc-pagecontent th {
   text-align: left;
   padding: 6px 12px;
 }
 #gc-pagecontent td {
   padding: 6px 12px;
   border: 1px solid #36C;
   vertical-align: top;
 }
 
+/* Provide an intro table for api reference docs. */
+#gc-pagecontent table.intro
+#gc-pagecontent table.intro th,
+#gc-pagecontent table.intro td {
+  border-collapse: separate;
+  border-style: none;
+}
+
+#gc-pagecontent table.intro {
+  padding: 0;
+}
+
+#gc-pagecontent table.intro th {
+  border-style: none;
+  padding: 6px 12px;
+  text-align: left;
+}
+
+#gc-pagecontent table.intro td {
+  border-bottom: 1px solid #E5E5E5;
+  padding: 6px 12px;
+  vertical-align: top;
+}
+
 /* Provide a "simple" version of the table to use just for layout. */
 #gc-pagecontent table.simple,
 #gc-pagecontent table.simple th,
 #gc-pagecontent table.simple td {
   border-collapse: separate;
   border-style: none;
 }
 #gc-pagecontent table.simple {
   padding: 0;
 }
@@ skipping 193 matching lines @@
 }
 
 .imaged li img {
   float: right;
   margin-bottom: 1em;
 }
 
 .imaged + p {
   clear: right;
 }