Docs: Add figure captions to images

Bug: 18334770
Change-Id: I4ed95bb638b6502129d59c099de9a0cd8b16ccb4
diff --git a/src/devices/bluetooth.jd b/src/devices/bluetooth.jd
index 62cf79d..f5e7363 100644
--- a/src/devices/bluetooth.jd
+++ b/src/devices/bluetooth.jd
@@ -2,7 +2,7 @@
 @jd:body
 
 <!--
-    Copyright 2013 The Android Open Source Project
+    Copyright 2014 The Android Open Source Project
 
     Licensed under the Apache License, Version 2.0 (the "License");
     you may not use this file except in compliance with the License.
@@ -32,7 +32,10 @@
 diagram shows the general structure of the Bluetooth stack:
 </p>
 
-<p><img src="images/bt.png"></p>
+<img src="images/bt.png" alt="Android Bluetooth architecture" id="figure1" />
+<p class="img-caption">
+  <strong>Figure 1.</strong> Bluetooth architecture
+</p>
 
 <dl>
   <dt>Application framework</dt>