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

device/nfc/nfc.mojom

 // Copyright 2015 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.
 
 // TODO(rockot): This should probably be moved to nfc.mojom.
 module device.nfc.mojom;
 
 enum NFCErrorType {
   SECURITY,
   NOT_SUPPORTED,
@@ skipping 48 matching lines @@
 };
 
 struct NFCMessage {
   // The body of the NFCMessage is a collection of NFCRecord objects.
   array<NFCRecord> data;
 
   // The |url| field is an ASCII serialized origin, optionally followed by a URL
   // path. It represents Web NFC id, that can be used for matching Web NFC
   // content with the filter specified by |url| field in NFCWatchOptions.
   string? url;
+
+  // Maximum size of NFC message that can be sent over IPC is 32KB.
+  const uint32 kMaxSize = 32768;

[Tom Sepez, 2016/11/21 18:12:34]

Where do we check this (on the receiving side)?

[shalamov, 2016/11/22 12:50:41]

It is in another CL: https://codereview.chromium.org/1765533004

device/nfc/android/java/src/org/chromium/device/nfc/NfcImpl.java
496 if (message.getByteArrayLength() > NfcMessage.MAX_SIZE)

Based on feedback from @haraken I'm splitting this CL. The mojom modifications
are in new CL: https://codereview.chromium.org/2524743002

 };
 
 struct NFCPushOptions {
   // The target of the push operation.
   NFCPushTarget target;
 
   // The timeout for the push operation, in milliseconds.
   double timeout;
 
   // If the property is true, the push operation will suspend active watchers
@@ skipping 47 matching lines @@
   // visibility or focus is lost.
   SuspendNFCOperations();
 
   // Resumes all suspended NFC operations.
   ResumeNFCOperations();
 };
 
 interface NFCClient {
   OnWatch(array<uint32> watch_ids, NFCMessage message);
 };