Credential Manager: Migrate to WebView client-based approach.

public/platform/WebCredentialManager.h

-// Copyright 2014 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 WebCredentialManager_h
-#define WebCredentialManager_h
-
-#include "public/platform/WebCallbacks.h"
-#include "public/platform/WebCredentialManagerError.h"
-#include "public/platform/WebString.h"
-#include "public/platform/WebVector.h"
-
-namespace blink {
-
-// WebCredentialManager provides an interface for asking Blink's embedder to
-// respond to `navigator.credentials.*` calls.
-class WebCredentialManager {
-public:
-    typedef WebCallbacks<WebCredential, WebCredentialManagerError> RequestCallbacks;
-    typedef WebCallbacks<void, WebCredentialManagerError> NotificationCallbacks;
-
-    WebCredentialManager() { }
-    virtual ~WebCredentialManager() { }
-
-    // Ownership of the callback is transferred to the callee for each of the following methods.
-    virtual void dispatchFailedSignIn(const WebCredential&, NotificationCallbacks*) { }
-    virtual void dispatchSignedIn(const WebCredential&, NotificationCallbacks*) { }
-    virtual void dispatchSignedOut(NotificationCallbacks*) { }
-    virtual void dispatchRequest(bool zeroClickOnly, const WebVector<WebURL>& federations, RequestCallbacks*) { }
-};
-
-} // namespace blink
-
-#endif // WebCredentialManager_h