Cast: Add tests for clocks being slow/fast

media/cast/test/fake_single_thread_task_runner.cc

Index: media/cast/test/fake_single_thread_task_runner.cc
diff --git a/media/cast/test/fake_single_thread_task_runner.cc b/media/cast/test/fake_single_thread_task_runner.cc
index d2950fd9fb6df2efe7fa9799709e4ead88ce927c..b60a1b12eafdfdf7b12952b567ec9b4ed2232a76 100644
--- a/media/cast/test/fake_single_thread_task_runner.cc
+++ b/media/cast/test/fake_single_thread_task_runner.cc
@@ -14,7 +14,8 @@ namespace test {
 
 FakeSingleThreadTaskRunner::FakeSingleThreadTaskRunner(
     base::SimpleTestTickClock* clock)
-    : clock_(clock) {}
+    : clock_(clock),
+      fail_on_next_task_(false) {}
 
 FakeSingleThreadTaskRunner::~FakeSingleThreadTaskRunner() {}
 
@@ -22,6 +23,9 @@ bool FakeSingleThreadTaskRunner::PostDelayedTask(
     const tracked_objects::Location& from_here,
     const base::Closure& task,
     base::TimeDelta delay) {
+  if (fail_on_next_task_) {
+    LOG(FATAL) << "Infinite task-add loop detected.";
+  }
   EXPECT_GE(delay, base::TimeDelta());
   PostedTask posed_task(from_here,
                         task,
@@ -38,7 +42,7 @@ bool FakeSingleThreadTaskRunner::RunsTasksOnCurrentThread() const {
 }
 
 void FakeSingleThreadTaskRunner::RunTasks() {
-  while(true) {
+  while (true) {
     // Run all tasks equal or older than current time.
     std::multimap<base::TimeTicks, PostedTask>::iterator it = tasks_.begin();
     if (it == tasks_.end())
@@ -53,6 +57,38 @@ void FakeSingleThreadTaskRunner::RunTasks() {
   }
 }
 
+void FakeSingleThreadTaskRunner::Sleep(base::TimeDelta t) {
+  base::TimeTicks run_until = clock_->NowTicks() + t;
+  while (1) {
+    // If we run more than 100000 iterations, we've probably
+    // hit some sort of case where a new task is posted every
+    // time that we invoke a task, and we can't make progress
+    // anymore. If that happens, set fail_on_next_task_ to true
+    // and throw an error when the next task is posted.
+    for (int i = 0; i < 100000; i++) {

[Alpha Left Google, 2014/05/16 18:20:51]

Do we actually run into this problem? It is suspicious that tasks are posted
continuously. 

[hubbe, 2014/05/16 18:24:56]

I did because of a bug in SkewedSingleThreadTaskRunner.

+      // Run all tasks equal or older than current time.
+      std::multimap<base::TimeTicks, PostedTask>::iterator it = tasks_.begin();
+      if (it == tasks_.end()) {
+        clock_->Advance(run_until - clock_->NowTicks());
+        return;
+      }
+
+      PostedTask task = it->second;
+      if (run_until < task.GetTimeToRun()) {
+        clock_->Advance(run_until - clock_->NowTicks());
+        return;
+      }
+
+      clock_->Advance(task.GetTimeToRun() - clock_->NowTicks());
+      tasks_.erase(it);
+      task.task.Run();
+    }
+    // Instead of failing immediately, we fail when the next task is
+    // added so that the backtrace will include the task that was added.
+    fail_on_next_task_ = true;
+  }
+}
+
 bool FakeSingleThreadTaskRunner::PostNonNestableDelayedTask(
     const tracked_objects::Location& from_here,
     const base::Closure& task,