Adding `content_security_policy` to a few sample extensions

chrome/common/extensions/docs/examples/api/processes/show_tabs/popup.css

Index: chrome/common/extensions/docs/examples/api/processes/show_tabs/popup.css
diff --git a/chrome/common/extensions/docs/examples/api/processes/show_tabs/popup.css b/chrome/common/extensions/docs/examples/api/processes/show_tabs/popup.css
new file mode 100644
index 0000000000000000000000000000000000000000..31e15e186ec74c2e64e6fac15e6d0975b683447e
--- /dev/null
+++ b/chrome/common/extensions/docs/examples/api/processes/show_tabs/popup.css
@@ -0,0 +1,25 @@
+/**
+ * Copyright (c) 2011 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.
+ */
+
+body {
+  overflow: hidden;
+  margin: 0px;
+  padding: 0px;
+  background: white;
+  width: 400px;
+}
+
+div:first-child {
+  margin-top: 0px;
+}
+
+div {
+  padding: 1px 3px;
+  font-family: sans-serif;
+  font-size: 10pt;
+  width: 400px;
+  margin-top: 1px;
+}