docs: Add developer guide cross-references, Project ACRE, round 4

Change-Id: I1b43414aaec8ea217b39a0d780c80a25409d0991
diff --git a/test-runner/src/android/test/ActivityInstrumentationTestCase2.java b/test-runner/src/android/test/ActivityInstrumentationTestCase2.java
index 24b125e..c4bcf31 100644
--- a/test-runner/src/android/test/ActivityInstrumentationTestCase2.java
+++ b/test-runner/src/android/test/ActivityInstrumentationTestCase2.java
@@ -37,6 +37,12 @@
  * New tests should be written using this base class.
  * 
  * <p>If you prefer an isolated unit test, see {@link android.test.ActivityUnitTestCase}.
+ *
+ * <div class="special reference">
+ * <h3>Developer Guides</h3>
+ * <p>For more information about application testing, read the
+ * <a href="{@docRoot}guide/topics/testing/index.html">Testing</a> developer guide.</p>
+ * </div>
  */
 public abstract class ActivityInstrumentationTestCase2<T extends Activity> 
         extends ActivityTestCase {