Remove dependency on cc::TestNowSource from scheduler code

content/child/scheduler/time_source.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/common/gpu/media/vp8_picture.h"
+#include "content/child/scheduler/time_source.h"
 
 namespace content {
 
-VP8Picture::VP8Picture() {
+TimeSource::TimeSource() {
 }
 
-VP8Picture::~VP8Picture() {
+TimeSource::~TimeSource() {
 }
 
-V4L2VP8Picture* VP8Picture::AsV4L2VP8Picture() {
-  return nullptr;
+base::TimeTicks TimeSource::Now() const {
+  return base::TimeTicks::Now();
 }
 
 }  // namespace content