Update Context.getSystemService() docs for download manager.

Change-Id: Ic514b3289b38d6da7d5fe4ffc87c6865280d66d8
diff --git a/core/java/android/content/Context.java b/core/java/android/content/Context.java
index 7951a30..aecdcb3 100644
--- a/core/java/android/content/Context.java
+++ b/core/java/android/content/Context.java
@@ -1206,6 +1206,8 @@
      * for management of input methods.
      * <dt> {@link #UI_MODE_SERVICE} ("uimode")
      * <dd> An {@link android.app.UiModeManager} for controlling UI modes.
+     * <dt> {@link #DOWNLOAD_SERVICE} ("download")
+     * <dd> A {@link android.net.DownloadManager} for requesting HTTP downloads
      * </dl>
      * 
      * <p>Note:  System services obtained via this API may be closely associated with
@@ -1253,6 +1255,8 @@
      * @see android.view.inputmethod.InputMethodManager
      * @see #UI_MODE_SERVICE
      * @see android.app.UiModeManager
+     * @see #DOWNLOAD_SERVICE
+     * @see android.net.DownloadManager
      */
     public abstract Object getSystemService(String name);