[Device Service] Decouple NFC implementation from //content

content/browser/nfc/nfc_host.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_BROWSER_NFC_NFC_HOST_H_

[Ted C, 2017/05/10 14:37:40]

In the same vein as the ifdef comments, should this be in
content/browser/android/nfc?  Or called NFCHostAndroid?

Without those, you'd need to look at the BUILD.gn file to see this is android
specific (or read the class level comment :-P)

[blundell, 2017/05/11 15:13:51]

Moved to //content/browser/android. Didn't put in a subdir there as there are no
others for native code.

+#define CONTENT_BROWSER_NFC_NFC_HOST_H_
+
+#include "base/android/jni_android.h"
+#include "content/public/browser/web_contents.h"
+#include "device/nfc/nfc_provider.mojom.h"
+
+namespace content {
+
+// On Android, NFC requires the Activity associated with the context in order to
+// access the NFC system APIs. NFCHost provides this functionality by mapping
+// NFC context IDs to the WebContents associated with those IDs.
+class NFCHost {
+ public:
+  explicit NFCHost(WebContents* web_contents);
+  ~NFCHost();
+
+  void GetNFC(device::nfc::mojom::NFCRequest request);
+
+ private:
+  // This instance's ID (passed to the NFC implementation via |nfc_provider_|
+  // and used from the implementation to map back to this object).
+  int id_;
+
+  // The WebContents that owns this instance.
+  WebContents* web_contents_;
+
+  device::nfc::mojom::NFCProviderPtr nfc_provider_;
+
+  base::android::ScopedJavaGlobalRef<jobject> java_nfc_host_;
+
+  DISALLOW_COPY_AND_ASSIGN(NFCHost);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_NFC_NFC_HOST_H_