[Try # 3] Scheduler refactoring to virtually eliminate redundant DoWorks

cc/test/ordered_simple_task_runner.cc

Index: cc/test/ordered_simple_task_runner.cc
diff --git a/cc/test/ordered_simple_task_runner.cc b/cc/test/ordered_simple_task_runner.cc
index 9dc4bbcd2dacb680d586699576a632e286aab037..161704fc45897fe97f643db91b94b3639b4c1936 100644
--- a/cc/test/ordered_simple_task_runner.cc
+++ b/cc/test/ordered_simple_task_runner.cc
@@ -137,6 +137,8 @@ bool OrderedSimpleTaskRunner::HasPendingTasks() const {
 }
 
 base::TimeTicks OrderedSimpleTaskRunner::NextTaskTime() {
+  RemoveCancelledTasks();
+
   if (pending_tasks_.size() <= 0) {
     return AbsoluteMaxNow();
   }
@@ -146,6 +148,7 @@ base::TimeTicks OrderedSimpleTaskRunner::NextTaskTime() {
 
 base::TimeDelta OrderedSimpleTaskRunner::DelayToNextTaskTime() {
   DCHECK(thread_checker_.CalledOnValidThread());
+  RemoveCancelledTasks();
 
   if (pending_tasks_.size() <= 0) {
     return AbsoluteMaxNow() - base::TimeTicks();
@@ -198,6 +201,11 @@ bool OrderedSimpleTaskRunner::RunTasksWhile(
   }
 
   while (pending_tasks_.size() > 0) {
+    // Skip canceled tasks.
+    if (pending_tasks_.begin()->task.IsCancelled()) {
+      pending_tasks_.erase(pending_tasks_.begin());
+      continue;
+    }
     // Check if we should continue to run pending tasks.
     bool condition_success = true;
     for (std::vector<base::Callback<bool(void)>>::iterator it =
@@ -344,4 +352,15 @@ bool OrderedSimpleTaskRunner::AdvanceNowCallback() {
   return true;
 }
 
+void OrderedSimpleTaskRunner::RemoveCancelledTasks() {
+  std::set<TestOrderablePendingTask>::iterator it = pending_tasks_.begin();
+  while (it != pending_tasks_.end()) {
+    if (it->task.IsCancelled()) {
+      it = pending_tasks_.erase(it);
+    } else {
+      it++;
+    }
+  }
+}
+
 }  // namespace cc