Flush SequenceWorkerPool tasks after each unit test.

base/test/task_runner_test_template.cc

Index: base/test/task_runner_test_template.cc
===================================================================
--- base/test/task_runner_test_template.cc	(revision 183651)
+++ base/test/task_runner_test_template.cc	(working copy)
@@ -8,7 +8,7 @@
 
 namespace internal {
 
-TaskTracker::TaskTracker() {}
+TaskTracker::TaskTracker() : task_runs_(0), task_runs_cv_(&lock_) {}
 
 TaskTracker::~TaskTracker() {}
 
@@ -17,18 +17,26 @@
 }
 
 void TaskTracker::RunTask(const Closure& task, int i) {
-  AutoLock lock(task_run_counts_lock_);
+  AutoLock lock(lock_);
   if (!task.is_null()) {
     task.Run();
   }
   ++task_run_counts_[i];
+  ++task_runs_;
+  task_runs_cv_.Signal();
 }
 
 std::map<int, int> TaskTracker::GetTaskRunCounts() const {
-  AutoLock lock(task_run_counts_lock_);
+  AutoLock lock(lock_);
   return task_run_counts_;
 }
 
+void TaskTracker::WaitForCountTasksToComplete(int count) {
+  AutoLock lock(lock_);
+  while (task_runs_ < count)
+    task_runs_cv_.Wait();
+}
+
 void ExpectRunsTasksOnCurrentThread(
     bool expected_value,
     const scoped_refptr<TaskRunner>& task_runner) {