PageLoadTiming fixes in prep for using base::Optional

components/page_load_metrics/renderer/BUILD.gn

 # 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.
 
 # GYP version: components/page_load_metrics.gypi:page_load_metrics_renderer
 static_library("renderer") {
   sources = [
     "metrics_render_frame_observer.cc",
     "metrics_render_frame_observer.h",
     "page_timing_metrics_sender.cc",
     "page_timing_metrics_sender.h",
   ]
   public_deps = [
     "//content/public/renderer",
   ]
   deps = [
     "//base",
     "//components/page_load_metrics/common",
     "//ipc",
     "//third_party/WebKit/public:blink",
     "//url",
   ]
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
+    "fake_page_timing_metrics_ipc_sender.cc",
+    "fake_page_timing_metrics_ipc_sender.h",
     "metrics_render_frame_observer_unittest.cc",
     "page_timing_metrics_sender_unittest.cc",
   ]
   deps = [
     ":renderer",
     "//base",
     "//components/page_load_metrics/common",
     "//ipc",
     "//testing/gmock",
     "//testing/gtest",
   ]
 }