[PageLoadMetrics] Remove legacy IPC from Page Load Metrics.

chrome/common/page_load_metrics/page_load_metrics_param_traits.h

-// Copyright (c) 2017 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_COMMON_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_PARAM_TRAITS_H_
-#define CHROME_COMMON_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_PARAM_TRAITS_H_
-
-#include "chrome/common/page_load_metrics/page_load_metrics.mojom.h"
-#include "ipc/ipc_message_utils.h"
-
-namespace IPC {
-
-// mojom::PageLoadTiming contains child mojom structs, which are stored in
-// mojo::StructPtr<>s. IPC doesn't have ParamTraits for mojo::StructPtr<>, so we
-// provide custom ParamTraits for PageLoadTiming here. This is temporary while
-// we run a field trial to verify there are no metric regressions due to
-// migrating to mojo, and will be removed once the field trial is complete and
-// shows expected results.
-template <>
-struct ParamTraits<page_load_metrics::mojom::PageLoadTiming> {
-  typedef page_load_metrics::mojom::PageLoadTiming param_type;
-  static void GetSize(base::PickleSizer* s, const param_type& p);
-  static void Write(base::Pickle* m, const param_type& p);
-  static bool Read(const base::Pickle* m,
-                   base::PickleIterator* iter,
-                   param_type* p);
-  static void Log(const param_type& p, std::string* l);
-};
-
-}  // namespace IPC
-
-#endif  // CHROME_COMMON_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_PARAM_TRAITS_H_