bluetooth: Layout tests for bluetooth error messages

LayoutTests/bluetooth/getCharacteristic.html

Index: LayoutTests/bluetooth/getCharacteristic.html
diff --git a/LayoutTests/bluetooth/getCharacteristic.html b/LayoutTests/bluetooth/getCharacteristic.html
index 403e7af4045284edcc3ad86b3b0a0813cf991b61..47bbdbb1bac7a8fb9b251136655424546861f07d 100644
--- a/LayoutTests/bluetooth/getCharacteristic.html
+++ b/LayoutTests/bluetooth/getCharacteristic.html
@@ -25,6 +25,7 @@ sequential_promise_test(function() {
       assert_unreached("Device went out of range, should fail.");
     }, function(e) {
       assert_equals(e.name, "NetworkError");
+      assert_equals(e.message, 'Bluetooth Device is no longer in range.');
     });
   });
 }, 'Device goes out of range. Reject with NetworkError.');