scheduler: Add an unthrottled per-frame task runner

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 356da5652cc55ee74e4a27cc7a27005e20f961d3..95debf05ce782a6035b78f033e4e289e03e76a17 100644
--- a/content/test/fake_renderer_scheduler.cc
+++ b/content/test/fake_renderer_scheduler.cc
@@ -50,6 +50,11 @@ scoped_refptr<scheduler::TaskQueue> FakeRendererScheduler::NewTimerTaskRunner(
   return nullptr;
 }
 
+scoped_refptr<scheduler::TaskQueue>
+FakeRendererScheduler::NewUnthrottledTaskRunner(const char* name) {
+  return nullptr;
+}
+
 std::unique_ptr<scheduler::RenderWidgetSchedulingState>
 FakeRendererScheduler::NewRenderWidgetSchedulingState() {
   return nullptr;