[Proximity Auth] Create one ProximityAuthClient per profile, rather than one global one.

chrome/browser/signin/chrome_proximity_auth_client.h

+// 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.
+
+#ifndef CHROME_BROWSER_SIGNIN_CHROME_PROXIMITY_AUTH_CLIENT_H_
+#define CHROME_BROWSER_SIGNIN_CHROME_PROXIMITY_AUTH_CLIENT_H_
+
+#include "base/macros.h"
+#include "components/keyed_service/core/keyed_service.h"
+#include "components/proximity_auth/proximity_auth_client.h"
+
+class Profile;
+
+// A Chrome-specific implementation of the ProximityAuthClient interface.
+// There is one |ChromeProximityAuthClient| per |Profile|.
+class ChromeProximityAuthClient : public proximity_auth::ProximityAuthClient,
+                                  public KeyedService {

[Tim Song, 2015/06/26 23:46:43]

Is there a benefit to making this ProximityAuthClient implementation a
KeyedService? What about initializing and storing it in the EasyUnlockService?

[Ilya Sherman, 2015/06/27 08:18:00]

Good idea!  Done.

+ public:
+  explicit ChromeProximityAuthClient(Profile* profile);
+  ~ChromeProximityAuthClient() override;
+
+  // proximity_auth::ProximityAuthClient:
+  std::string GetAuthenticatedUsername() const override;
+  void Lock() override;
+
+ private:
+  Profile* const profile_;
+
+  DISALLOW_COPY_AND_ASSIGN(ChromeProximityAuthClient);
+};
+
+#endif  // CHROME_BROWSER_SIGNIN_CHROME_PROXIMITY_AUTH_CLIENT_H_