bluetooth: Blink-side implementation of getCharacteristic.

Source/modules/bluetooth/BluetoothGATTService.h

Index: Source/modules/bluetooth/BluetoothGATTService.h
diff --git a/Source/modules/bluetooth/BluetoothGATTService.h b/Source/modules/bluetooth/BluetoothGATTService.h
index 146f9ed6880a23d40ced338440462dfa08da885b..d1a1ca3f3920ce127d029efec0f144afa2c748d9 100644
--- a/Source/modules/bluetooth/BluetoothGATTService.h
+++ b/Source/modules/bluetooth/BluetoothGATTService.h
@@ -12,7 +12,9 @@
 
 namespace blink {
 
+class ScriptPromise;
 class ScriptPromiseResolver;
+class ScriptState;
 
 // Represents a GATT Service within a Bluetooth Peripheral, a collection of
 // characteristics and relationships to other services that encapsulate the
@@ -40,6 +42,7 @@ public:
     // IDL exposed interface:
     String uuid() { return m_webService->uuid; }
     bool isPrimary() { return m_webService->isPrimary; }
+    ScriptPromise getCharacteristic(ScriptState*, String characteristicUUID);
 
 private:
     OwnPtr<WebBluetoothGATTService> m_webService;