Implement PostDelayedTaskAt for guaranteed timer ordering

content/test/fake_renderer_scheduler.cc

Index: content/test/fake_renderer_scheduler.cc
diff --git a/content/test/fake_renderer_scheduler.cc b/content/test/fake_renderer_scheduler.cc
index 2a3fe408e23405ea8f72ac45d507463231527537..94960dd830dd708b85217c3d919b8875947093c5 100644
--- a/content/test/fake_renderer_scheduler.cc
+++ b/content/test/fake_renderer_scheduler.cc
@@ -12,8 +12,7 @@ FakeRendererScheduler::FakeRendererScheduler() {
 FakeRendererScheduler::~FakeRendererScheduler() {
 }
 
-scoped_refptr<base::SingleThreadTaskRunner>
-FakeRendererScheduler::DefaultTaskRunner() {
+scoped_refptr<scheduler::TaskQueue> FakeRendererScheduler::DefaultTaskRunner() {
   return nullptr;
 }
 
@@ -32,8 +31,7 @@ FakeRendererScheduler::IdleTaskRunner() {
   return nullptr;
 }
 
-scoped_refptr<base::SingleThreadTaskRunner>
-FakeRendererScheduler::TimerTaskRunner() {
+scoped_refptr<scheduler::TaskQueue> FakeRendererScheduler::TimerTaskRunner() {
   return nullptr;
 }