Flush SequenceWorkerPool tasks after each unit test.

base/test/sequenced_task_runner_test_template.cc

Index: base/test/sequenced_task_runner_test_template.cc
===================================================================
--- base/test/sequenced_task_runner_test_template.cc	(revision 186525)
+++ base/test/sequenced_task_runner_test_template.cc	(working copy)
@@ -16,7 +16,10 @@
   : i(i), type(type) {
 }
 
-SequencedTaskTracker::SequencedTaskTracker() : next_post_i_(0) {
+SequencedTaskTracker::SequencedTaskTracker()
+    : next_post_i_(0),
+      task_end_count_(0),
+      task_end_cv_(&lock_) {
 }
 
 void SequencedTaskTracker::PostWrappedNonNestableTask(
@@ -81,6 +84,8 @@
 void SequencedTaskTracker::TaskEnded(int i) {
   AutoLock lock(lock_);
   events_.push_back(TaskEvent(i, TaskEvent::END));
+  ++task_end_count_;
+  task_end_cv_.Signal();
 }
 
 const std::vector<TaskEvent>&
@@ -88,6 +93,12 @@
   return events_;
 }
 
+void SequencedTaskTracker::WaitForCompletedTasks(int count) {
+  AutoLock lock(lock_);
+  while (task_end_count_ < count)
+    task_end_cv_.Wait();
+}
+
 SequencedTaskTracker::~SequencedTaskTracker() {
 }