bluetooth: Add BluetoothGATTCharacteristic IDL and Blink interface

public/platform/modules/bluetooth/WebBluetooth.h

Index: public/platform/modules/bluetooth/WebBluetooth.h
diff --git a/public/platform/modules/bluetooth/WebBluetooth.h b/public/platform/modules/bluetooth/WebBluetooth.h
index 1a22f2ef84c9ce984854cfad176baeb1b140b002..8dd3d4944cf6788985ba2dea9b7d3ea23fb5ba4c 100644
--- a/public/platform/modules/bluetooth/WebBluetooth.h
+++ b/public/platform/modules/bluetooth/WebBluetooth.h
@@ -12,19 +12,26 @@ namespace blink {
 
 struct WebBluetoothDevice;
 struct WebBluetoothError;
+struct WebBluetoothGATTCharacteristic;
 struct WebBluetoothGATTRemoteServer;
 struct WebBluetoothGATTService;
 
 // Success and failure callbacks for requestDevice.
-// WebBluetoothDevice and WebBluetoothError object ownership is transfered.
+// WebBluetoothDevice and WebBluetoothError object ownership is transferred.
 typedef WebCallbacks<WebBluetoothDevice, WebBluetoothError> WebBluetoothRequestDeviceCallbacks;
 
 // Success and failure callbacks for connectGATT.
+// WebBluetoothGATTRemoteServer and WebBluetoothError object ownership is transferred.
 typedef WebCallbacks<WebBluetoothGATTRemoteServer, WebBluetoothError> WebBluetoothConnectGATTCallbacks;
 
 // Success and failure callbacks for getPrimaryService.
+// WebBluetoothGATTService and WebBluetoothError object ownership is transferred.
 typedef WebCallbacks<WebBluetoothGATTService, WebBluetoothError> WebBluetoothGetPrimaryServiceCallbacks;
 
+// Success and failure callbacks for getCharacteristic.
+// WebBluetoothCharacteristic and WebBluetoothError object ownership is transferred.
+typedef WebCallbacks<WebBluetoothGATTCharacteristic, WebBluetoothError> WebBluetoothGetCharacteristicCallbacks;
+
 class WebBluetooth {
 public:
     virtual ~WebBluetooth() { }
@@ -47,6 +54,12 @@ public:
         const WebString& serviceUUID,
         WebBluetoothGetPrimaryServiceCallbacks*) { }
     // virtual void getPrimaryServices() { }
+
+    // BluetoothGATTService methods:
+    // See https://webbluetoothcg.github.io/web-bluetooth/#idl-def-bluetoothgattservice
+    virtual void getCharacteristic(const WebString& serviceInstanceID,
+        const WebString& characteristicUUID,
+        WebBluetoothGetCharacteristicCallbacks*) { }
 };
 
 } // namespace blink