bluetooth: Add control for reading/writing of characteristics to internals page.

chrome/browser/resources/bluetooth_internals/bluetooth_internals.css

 /* Copyright 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.
  */
 
 :root {
   --expandable-list-item-border: 1px solid gray;
   --fade-duration: 225ms;
   --header-height: 48px;
   --md-timing-function: cubic-bezier(.4, 0, .6, 1);
@@ skipping 381 matching lines @@
   .flex {
     display: flex;
   }
 }
 
 /* Device Details Page */
 .device-details-page section,
 .info-container fieldset {
   -webkit-margin-start: 1em;
 }
+
+/* Value Control */
+.value-control > div {
+  display: flex;
+  margin: 4px 0;
+}
+
+.value-control > div > input {
+  flex-grow: 1;
+}
+
+.value-control > div:nth-of-type(2) {
+  justify-content: flex-end;
+}