Implement WebBluetooth descriptor.readValue()

third_party/WebKit/public/platform/modules/bluetooth/web_bluetooth.mojom

Index: third_party/WebKit/public/platform/modules/bluetooth/web_bluetooth.mojom
diff --git a/third_party/WebKit/public/platform/modules/bluetooth/web_bluetooth.mojom b/third_party/WebKit/public/platform/modules/bluetooth/web_bluetooth.mojom
index 148e756e94deb4db78a5fe81ef9a98ff23e6bf84..a982d1796b34cfec714e378c2cdcbee17f65b61c 100644
--- a/third_party/WebKit/public/platform/modules/bluetooth/web_bluetooth.mojom
+++ b/third_party/WebKit/public/platform/modules/bluetooth/web_bluetooth.mojom
@@ -103,6 +103,7 @@ enum WebBluetoothResult {
   REQUEST_DEVICE_WITH_BLOCKLISTED_UUID,
   REQUEST_DEVICE_FROM_CROSS_ORIGIN_IFRAME,
   REQUEST_DEVICE_WITHOUT_FRAME,
+  DESCRIPTOR_NO_LONGER_EXISTS,
 };
 
 struct WebBluetoothScanFilter {
@@ -239,6 +240,22 @@ interface WebBluetoothService {
     bluetooth.mojom.UUID? descriptor_uuid) => (
       WebBluetoothResult result,
       array<WebBluetoothRemoteGATTDescriptor>? descriptors);
+
+  // Reads the value for descriptor with |descriptor_instance_id|.

[ortuno, 2017/01/20 04:30:53]

I think you wrote this comment twice?

[dougt, 2017/01/23 21:40:37]

Done.

+  // If the value is successfully read the callback will be run with
+  // WebBluetoothResult::SUCCESS and the descriptor's value. If the value is not
+  // successfully read the callback with be run with the corresponding error and
+  // nullptr for value.
+
+  // Reads the value for the descriptor identified by
+  // |descriptor_instance_id|. If the value is successfully read the callback
+  // will be run with WebBluetoothResult::SUCCESS and the descriptor's value. If
+  // the value is not successfully read the callback with be run with the
+  // corresponding error and nullptr for value

[ortuno, 2017/01/20 04:30:53]

nit: Shouldn't this be nullopt.

[dougt, 2017/01/23 21:40:37]

Not sure.  On the C++ binding side, the callback is going to be called with an
Optional<Vector<uint8_t>>. I think when its not set (and when the result !=
SUCCESS), the value is testable with is_null.  Vince, do you know the answer
here since you just updated these docs?

+  RemoteDescriptorReadValue(
+    string descriptor_instance_id) => (
+    WebBluetoothResult result,
+    array<uint8>? value);
 };
 
 // Classes should implement this interface and pass an associated pointer