bluetooth: Explain why standard names aren't recognized in error message.

LayoutTests/bluetooth/getCharacteristic.html

Index: LayoutTests/bluetooth/getCharacteristic.html
diff --git a/LayoutTests/bluetooth/getCharacteristic.html b/LayoutTests/bluetooth/getCharacteristic.html
index 3f90f4954b1fb98215496a15b25911f28dbdb068..fdd6762f2be97f1e6a043848cce1a1ea020b2b5a 100644
--- a/LayoutTests/bluetooth/getCharacteristic.html
+++ b/LayoutTests/bluetooth/getCharacteristic.html
@@ -109,7 +109,13 @@ promise_test(() => {
           name: 'SyntaxError',
           message: 'Failed to execute \'getCharacteristic\' on ' +
                    '\'BluetoothGATTService\': \Invalid Characteristic name: ' +
-                   '\'wrong_name\'.'
+                   '\'wrong_name\'. ' +
+                   'It must be a valid UUID alias (e.g. 0x1234), ' +
+                   'UUID (lowercase hex characters e.g. ' +
+                   '\'00001234-0000-1000-8000-00805f9b34fb\'), ' +
+                   'or recognized standard name from ' +
+                   'https://developer.bluetooth.org/gatt/characteristics/Pages/CharacteristicsHome.aspx' +
+                   ' e.g. \'aerobic_heart_rate_lower_limit\'.'
         }, 'Wrong Characteristic name passed.');
     });
 }, 'Wrong Characteristic name. Reject with SyntaxError.');