Small NFC API docs addition.

Indicate that if the device does not support Bluetooth or WiFI,
calling the API is a no-op.

Bug: 6620788
Change-Id: Ib261e0e7855d0914e97803b3b808015b72f3a186

Author: Martijn Coenen

core/java/android/nfc/NfcAdapter.java

@@ -637,6 +637,9 @@ public boolean disable() {
      * {@link Activity#onDestroy}. This is guaranteed if you call this API
      * during {@link Activity#onCreate}.
      *
+     * <p class="note">If this device does not support alternate transports
+     * such as Bluetooth or WiFI, calling this method does nothing.
+     *
      * <p class="note">Requires the {@link android.Manifest.permission#NFC} permission.
      *
      * @param uris an array of Uri(s) to push over Android Beam
@@ -711,6 +714,9 @@ public void setBeamPushUris(Uri[] uris, Activity activity) {
      * {@link Activity#onDestroy}. This is guaranteed if you call this API
      * during {@link Activity#onCreate}.
      *
+     * <p class="note">If this device does not support alternate transports
+     * such as Bluetooth or WiFI, calling this method does nothing.
+     *
      * <p class="note">Requires the {@link android.Manifest.permission#NFC} permission.
      *
      * @param callback callback, or null to disable