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

chrome/browser/signin/chrome_proximity_auth_client.h

Index: chrome/browser/signin/chrome_proximity_auth_client.h
diff --git a/chrome/browser/signin/chrome_proximity_auth_client.h b/chrome/browser/signin/chrome_proximity_auth_client.h
new file mode 100644
index 0000000000000000000000000000000000000000..72748204ed54e877b630fe9b85f9c43c5fe8961b
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+++ b/chrome/browser/signin/chrome_proximity_auth_client.h
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+// 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/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:
+  explicit ChromeProximityAuthClient(Profile* profile);
+  ~ChromeProximityAuthClient() override;
+
+  // proximity_auth::ProximityAuthClient:
+  std::string GetAuthenticatedUsername() const override;
+
+ private:
+  Profile* const profile_;
+
+  DISALLOW_COPY_AND_ASSIGN(ChromeProximityAuthClient);
+};
+
+#endif  // CHROME_BROWSER_SIGNIN_CHROME_PROXIMITY_AUTH_CLIENT_H_