[webnfc] Implement nfc.watch in blink nfc module.

third_party/WebKit/Source/modules/nfc/NFC.h

Index: third_party/WebKit/Source/modules/nfc/NFC.h
diff --git a/third_party/WebKit/Source/modules/nfc/NFC.h b/third_party/WebKit/Source/modules/nfc/NFC.h
index 60c799562a2a4e22a0777a8cd55065ebbe7174ee..63211947124eb1f5e5520f37aaa6b78e40f7579f 100644
--- a/third_party/WebKit/Source/modules/nfc/NFC.h
+++ b/third_party/WebKit/Source/modules/nfc/NFC.h
@@ -11,7 +11,9 @@
 #include "bindings/modules/v8/UnionTypesModules.h"
 #include "core/page/PageLifecycleObserver.h"
 #include "device/nfc/nfc.mojom-wtf.h"
+#include "modules/nfc/MessageCallback.h"
 #include "mojo/public/cpp/bindings/binding.h"
+#include "wtf/HashMap.h"
 
 namespace blink {
 
@@ -19,6 +21,7 @@ class MessageCallback;
 class NFCError;
 class NFCPushOptions;
 using NFCPushMessage = StringOrArrayBufferOrNFCMessage;
+class NFCWatchCallback;
 class NFCWatchOptions;
 class ServiceRegistry;
 
@@ -58,15 +61,23 @@ public:
     DECLARE_VIRTUAL_TRACE();
 
 private:
+    friend class NFCWatchCallback;
     bool Initialize(ServiceRegistry*);
+
+    // Returns promise with DOMException if feature is not supported
+    // or when context is not secure. Otherwise, returns empty promise.
+    ScriptPromise RejectIfNotSupported(ScriptState*);
     void OnError();
     // device::wtf::NFCClient implementation
     void OnWatch(uint32_t id, device::wtf::NFCMessagePtr) override;
+    void OnWatchRegistered(uint32_t id, MessageCallback*);
 
 private:
     explicit NFC(LocalFrame*);
     device::wtf::NFCPtr m_nfc;
     mojo::Binding<device::wtf::NFCClient> m_client;
+    using WatchCallbacksMap = HeapHashMap<uint32_t, Member<MessageCallback>>;
+    WatchCallbacksMap m_callbacks;
 };
 
 } // namespace blink