Implement WebBluetooth getDescriptor[s]

third_party/WebKit/LayoutTests/bluetooth/script-tests/characteristic/descriptor-get-same-object.js

+'use strict';
+promise_test(() => {
+  return setBluetoothFakeAdapter('DisconnectingHealthThermometerAdapter')
+    .then(() => requestDeviceWithKeyDown({
+      filters: [{services: ['health_thermometer']}]}))
+    .then(device => device.gatt.connect())
+    .then(gattServer => gattServer.getPrimaryService('health_thermometer'))
+    .then(service => service.getCharacteristic('measurement_interval'))
+    .then(characteristic => Promise.all([
+      characteristic.CALLS([
+        getDescriptor(user_description.name)|

[ortuno, 2016/12/07 08:05:12]

We want to test that all argument variations i.e. number, name, full uuid
string, are able to find the descriptor. Similar to
https://cs.chromium.org/chromium/src/third_party/WebKit/LayoutTests/bluetooth...

[dougt, 2016/12/07 19:48:57]

Done.

+        getDescriptors()|
+        getDescriptors(user_description.name)[UUID]]),
+      characteristic.PREVIOUS_CALL]))
+    .then(descriptors_arrays => {
+      // Convert to arrays if necessary.
+      for (let i = 0; i < descriptors_arrays.length; i++) {
+        descriptors_arrays[i] = [].concat(descriptors_arrays[i]);
+      }
+
+      for (let i = 1; i < descriptors_arrays.length; i++) {
+        assert_equals(descriptors_arrays[0].length,
+                      descriptors_arrays[i].length);
+      }
+
+      let base_set = new Set(descriptors_arrays[0]);
+      for (let descriptors of descriptors_arrays) {
+        descriptors.forEach(

[ortuno, 2016/12/07 08:05:12]

Also we are not really checking what happens when a descriptor is not found.

[dougt, 2016/12/07 19:48:57]

We are checking that all calls return identical results.  If they all return
empty sets this test will pass.  I will add a test to ensure that
descriptors_arrays is not empty.

[ortuno, 2016/12/08 05:42:51]

Good thing to add to the test but I was thinking something more like the
following test:
https://cs.chromium.org/chromium/src/third_party/WebKit/LayoutTests/bluetooth...

We need to be sure that the error message: 'No Descriptors with specified UUID
found in Characteristic' is actually being returned if the descriptor is not in
the device.

+          descriptor => assert_true(base_set.has(descriptor)));
+      }
+    });
+}, 'Calls to FUNCTION_NAME should return the same object.');