scheduler: Implement task observers

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 86bf4a2a515b35ddcf578a412412666c306dce97..5deb2880c2fb10388aa42a5c39e0143acb3280bf 100644
--- a/content/test/fake_renderer_scheduler.cc
+++ b/content/test/fake_renderer_scheduler.cc
@@ -56,6 +56,14 @@ bool FakeRendererScheduler::ShouldYieldForHighPriorityWork() {
   return false;
 }
 
+void FakeRendererScheduler::AddTaskObserver(
+    base::MessageLoop::TaskObserver* task_observer) {
+}
+
+void FakeRendererScheduler::RemoveTaskObserver(
+    base::MessageLoop::TaskObserver* task_observer) {
+}
+
 void FakeRendererScheduler::Shutdown() {
 }