servo: Merge #12261 - Missing steps of Characteristic's readValue, writeValue functions (from szeged:gattcharacteristicfunctions); r=jdm

<!-- Please describe your changes on the following line: -->
Add a check for the read property of the characteristic as described in https://webbluetoothcg.github.io/web-bluetooth/#dom-bluetoothremotegattcharacteristic-readvalue (Step 4.1)
Add two missing steps to characteristic's WriteValue function. https://webbluetoothcg.github.io/web-bluetooth/#dom-bluetoothremotegattcharacteristic-writevalue (Step 4 and 5)

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes do not require tests because, there are no Web Bluetooth test API implementation yet.

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

Source-Repo: https://github.com/servo/servo
Source-Revision: 7da28b7ca63c7b4538aa1b81b7ad1182415c32f2

servo/components/script/dom/bindings/error.rs

@@ -57,6 +57,8 @@ pub enum Error {
     QuotaExceeded,
     /// TypeMismatchError DOMException
     TypeMismatch,
+    /// InvalidModificationError DOMException
+    InvalidModification,
 
     /// TypeError JavaScript Error
     Type(String),
@@ -97,6 +99,7 @@ pub unsafe fn throw_dom_exception(cx: *mut JSContext, global: GlobalRef, result:
         Error::NoModificationAllowed => DOMErrorName::NoModificationAllowedError,
         Error::QuotaExceeded => DOMErrorName::QuotaExceededError,
         Error::TypeMismatch => DOMErrorName::TypeMismatchError,
+        Error::InvalidModification => DOMErrorName::InvalidModificationError,
         Error::Type(message) => {
             assert!(!JS_IsExceptionPending(cx));
             throw_type_error(cx, &message);

servo/components/script/dom/bluetoothremotegattcharacteristic.rs

@@ -4,13 +4,15 @@
 
 use bluetooth_blacklist::{Blacklist, uuid_is_blacklisted};
 use dom::bindings::cell::DOMRefCell;
+use dom::bindings::codegen::Bindings::BluetoothCharacteristicPropertiesBinding::
+    BluetoothCharacteristicPropertiesMethods;
 use dom::bindings::codegen::Bindings::BluetoothDeviceBinding::BluetoothDeviceMethods;
 use dom::bindings::codegen::Bindings::BluetoothRemoteGATTCharacteristicBinding;
 use dom::bindings::codegen::Bindings::BluetoothRemoteGATTCharacteristicBinding::
     BluetoothRemoteGATTCharacteristicMethods;
 use dom::bindings::codegen::Bindings::BluetoothRemoteGATTServerBinding::BluetoothRemoteGATTServerMethods;
 use dom::bindings::codegen::Bindings::BluetoothRemoteGATTServiceBinding::BluetoothRemoteGATTServiceMethods;
-use dom::bindings::error::Error::{Network, Security, Type};
+use dom::bindings::error::Error::{InvalidModification, Network, NotSupported, Security, Type};
 use dom::bindings::error::{Fallible, ErrorResult};
 use dom::bindings::global::GlobalRef;
 use dom::bindings::js::{JS, MutHeap, Root};
@@ -23,6 +25,10 @@ use dom::bluetoothuuid::{BluetoothDescriptorUUID, BluetoothUUID};
 use ipc_channel::ipc::{self, IpcSender};
 use net_traits::bluetooth_thread::BluetoothMethodMsg;
 
+// Maximum length of an attribute value.
+// https://www.bluetooth.org/DocMan/handlers/DownloadDoc.ashx?doc_id=286439 (Vol. 3, page 2169)
+const MAXIMUM_ATTRIBUTE_LENGTH: usize = 512;
+
 // https://webbluetoothcg.github.io/web-bluetooth/#bluetoothremotegattcharacteristic
 #[dom_struct]
 pub struct BluetoothRemoteGATTCharacteristic {
@@ -160,6 +166,9 @@ impl BluetoothRemoteGATTCharacteristicMethods for BluetoothRemoteGATTCharacteris
         if !self.Service().Device().Gatt().Connected() {
             return Err(Network)
         }
+        if !self.Properties().Read() {
+            return Err(NotSupported)
+        }
         self.get_bluetooth_thread().send(
             BluetoothMethodMsg::ReadValue(self.get_instance_id(), sender)).unwrap();
         let result = receiver.recv().unwrap();
@@ -180,6 +189,12 @@ impl BluetoothRemoteGATTCharacteristicMethods for BluetoothRemoteGATTCharacteris
         if uuid_is_blacklisted(self.uuid.as_ref(), Blacklist::Writes) {
             return Err(Security)
         }
+        if value.len() > MAXIMUM_ATTRIBUTE_LENGTH {
+            return Err(InvalidModification)
+        }
+        if !self.Service().Device().Gatt().Connected() {
+            return Err(Network)
+        }
         let (sender, receiver) = ipc::channel().unwrap();
         self.get_bluetooth_thread().send(
             BluetoothMethodMsg::WriteValue(self.get_instance_id(), value, sender)).unwrap();