bluetooth: Refactor GetDescriptorForUUID to GetDescriptorsForUUID.

device/bluetooth/bluetooth_remote_gatt_characteristic_android.cc

Index: device/bluetooth/bluetooth_remote_gatt_characteristic_android.cc
diff --git a/device/bluetooth/bluetooth_remote_gatt_characteristic_android.cc b/device/bluetooth/bluetooth_remote_gatt_characteristic_android.cc
index bb7e6696e7e55bfd7a930321243befbdd1541970..b4ecc88e6c62e2301e9561722615de9b17562b11 100644
--- a/device/bluetooth/bluetooth_remote_gatt_characteristic_android.cc
+++ b/device/bluetooth/bluetooth_remote_gatt_characteristic_android.cc
@@ -155,10 +155,10 @@ void BluetoothRemoteGattCharacteristicAndroid::StartNotifySession(
     return;
   }
 
-  BluetoothGattDescriptor* descriptor = GetDescriptorForUUID(
+  std::vector<BluetoothGattDescriptor*> ccc_descriptor = GetDescriptorsForUUID(
       BluetoothGattDescriptor::ClientCharacteristicConfigurationUuid());
 
-  if (!descriptor) {
+  if (ccc_descriptor.size() != 1u) {

[ortuno, 2016/03/13 20:41:45]

Hmm this would fail with GATT NOT SUPPORTED if the characteristic has two ccc
descriptors. I'm OK with it failing with if there are 2 CCC descriptors but GATT
NOT SUPPORTED is misleading.

[scheib, 2016/03/25 00:13:57]

Done: Different errors returned for <1 and >1. Test added for multiple CCCDs.

     LOG(ERROR)
         << "Could not find client characteristic configuration descriptor";
     base::MessageLoop::current()->PostTask(
@@ -183,7 +183,7 @@ void BluetoothRemoteGattCharacteristicAndroid::StartNotifySession(
   value.push_back(0);
 
   pending_start_notify_calls_.push(std::make_pair(callback, error_callback));
-  descriptor->WriteRemoteDescriptor(
+  ccc_descriptor[0]->WriteRemoteDescriptor(
       value, base::Bind(&BluetoothRemoteGattCharacteristicAndroid::
                             OnStartNotifySessionSuccess,
                         base::Unretained(this)),