bluetooth: Implement getAvailability()

This change implements the getAvailability() method for
navigator.bluetooth as defined in the specification.

Bug: 707640
Change-Id: I9e9b3e7f8ea7f259e975f71cb6d9570e5f04b479
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1651516
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Ovidio de Jesús Ruiz-Henríquez <odejesush@chromium.org>
Auto-Submit: Ovidio de Jesús Ruiz-Henríquez <odejesush@chromium.org>
Cr-Commit-Position: refs/heads/master@{#688987}
void FakeCentral::GetLastWrittenDescriptorValue(
    const std::string& descriptor_id,
    const std::string& characteristic_id,
    const std::string& service_id,
    const std::string& peripheral_address,
    GetLastWrittenDescriptorValueCallback callback) {
  FakeRemoteGattDescriptor* fake_remote_gatt_descriptor =
      GetFakeRemoteGattDescriptor(peripheral_address, service_id,
                                  characteristic_id, descriptor_id);
  if (!fake_remote_gatt_descriptor) {
    std::move(callback).Run(false, base::nullopt);
  }

  std::move(callback).Run(true,
                          fake_remote_gatt_descriptor->last_written_value());
}

void FakeCentral::GetLastWrittenDescriptorValue(
    const std::string& descriptor_id,
    const std::string& characteristic_id,
    const std::string& service_id,
    const std::string& peripheral_address,
    GetLastWrittenDescriptorValueCallback callback) {
  FakeRemoteGattDescriptor* fake_remote_gatt_descriptor =
      GetFakeRemoteGattDescriptor(peripheral_address, service_id,
                                  characteristic_id, descriptor_id);
  if (!fake_remote_gatt_descriptor) {
    std::move(callback).Run(false, base::nullopt);
  }

  std::move(callback).Run(true,
                          fake_remote_gatt_descriptor->last_written_value());
}
