Auto merge of #15368 - szeged:get_availability, r=nox

Implement GetAvailability for Bluetooth

<!-- Please describe your changes on the following line: -->
This implements the [getAvailability](https://webbluetoothcg.github.io/web-bluetooth/#dom-bluetooth-getavailability) function from the spec.

---
<!-- 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
- [ ] These changes fix #__ (github issue number if applicable).

<!-- Either: -->
- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/15368)
<!-- Reviewable:end -->

components/bluetooth/lib.rs

@@ -246,13 +246,16 @@ impl BluetoothManager {
                 },
                 BluetoothRequest::Test(data_set_name, sender) => {
                     let _ = sender.send(self.test(data_set_name));
-                }
+                },
                 BluetoothRequest::SetRepresentedToNull(service_ids, characteristic_ids, descriptor_ids) => {
                     self.remove_ids_from_caches(service_ids, characteristic_ids, descriptor_ids)
-                }
+                },
                 BluetoothRequest::IsRepresentedDeviceNull(id, sender) => {
                     let _ = sender.send(!self.device_is_cached(&id));
-                }
+                },
+                BluetoothRequest::GetAvailability(sender) => {
+                    let _ = sender.send(self.get_availability());
+                },
                 BluetoothRequest::Exit => {
                     break
                 },
@@ -924,4 +927,9 @@ impl BluetoothManager {
         // TODO: Implement this when supported in lower level
         return Err(BluetoothError::NotSupported);
     }
+
+    // https://webbluetoothcg.github.io/web-bluetooth/#dom-bluetooth-getavailability
+    fn get_availability(&mut self) -> BluetoothResponseResult {
+        Ok(BluetoothResponse::GetAvailability(self.get_adapter().is_ok()))
+    }
 }

components/bluetooth_traits/lib.rs

@@ -91,6 +91,7 @@ pub enum BluetoothRequest {
     WatchAdvertisements(String, IpcSender<BluetoothResponseResult>),
     SetRepresentedToNull(Vec<String>, Vec<String>, Vec<String>),
     IsRepresentedDeviceNull(String, IpcSender<bool>),
+    GetAvailability(IpcSender<BluetoothResponseResult>),
     Test(String, IpcSender<BluetoothResult<()>>),
     Exit,
 }
@@ -107,4 +108,5 @@ pub enum BluetoothResponse {
     WriteValue(Vec<u8>),
     EnableNotification(()),
     WatchAdvertisements(()),
+    GetAvailability(bool),
 }

components/script/dom/bluetooth.rs

@@ -443,6 +443,18 @@ impl BluetoothMethods for Bluetooth {
         return p;
     }
 
+    #[allow(unrooted_must_root)]
+    // https://webbluetoothcg.github.io/web-bluetooth/#dom-bluetooth-getavailability
+    fn GetAvailability(&self) -> Rc<Promise> {
+        let p = Promise::new(&self.global());
+        // Step 1. We did not override the method
+        // Step 2 - 3. in handle_response
+        let sender = response_async(&p, self);
+        self.get_bluetooth_thread().send(
+            BluetoothRequest::GetAvailability(sender)).unwrap();
+        p
+    }
+
     // https://webbluetoothcg.github.io/web-bluetooth/#dom-bluetooth-onavailabilitychanged
     event_handler!(availabilitychanged, GetOnavailabilitychanged, SetOnavailabilitychanged);
 }
@@ -466,6 +478,11 @@ impl AsyncBluetoothListener for Bluetooth {
                 // Step 5.
                 promise.resolve_native(promise_cx, &bt_device);
             },
+            // https://webbluetoothcg.github.io/web-bluetooth/#dom-bluetooth-getavailability
+            // Step 2 - 3.
+            BluetoothResponse::GetAvailability(is_available) => {
+                promise.resolve_native(promise_cx, &is_available);
+            }
             _ => promise.reject_error(promise_cx, Error::Type("Something went wrong...".to_owned())),
         }
     }

components/script/dom/webidls/Bluetooth.webidl

@@ -29,8 +29,8 @@ dictionary RequestDeviceOptions {
 
 [Pref="dom.bluetooth.enabled"]
 interface Bluetooth : EventTarget {
-  // [SecureContext]
-  // Promise<boolean> getAvailability();
+  [SecureContext]
+  Promise<boolean> getAvailability();
   [SecureContext]
   attribute EventHandler onavailabilitychanged;
   // [SecureContext, SameObject]