[Presentation API] Remove references to presentation sessions.

content/public/common/presentation_session.cc

-// 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.
-
-#include "content/public/common/presentation_session.h"
-
-namespace content {
-
-PresentationSessionInfo::PresentationSessionInfo(
-    const GURL& presentation_url,
-    const std::string& presentation_id)
-    : presentation_url(presentation_url), presentation_id(presentation_id) {}
-
-PresentationSessionInfo::~PresentationSessionInfo() {
-}
-
-PresentationError::PresentationError(
-    PresentationErrorType error_type,
-    const std::string& message)
-    : error_type(error_type),
-      message(message) {
-}
-
-PresentationError::~PresentationError() {
-}
-
-}  // namespace content
-