TaskScheduler [12] Support SINGLE_THREADED in SchedulerThreadPool DO NOT SUBMIT

base/task_scheduler/scheduler_thread_pool_unittest.cc

Index: base/task_scheduler/scheduler_thread_pool_unittest.cc
diff --git a/base/task_scheduler/scheduler_thread_pool_unittest.cc b/base/task_scheduler/scheduler_thread_pool_unittest.cc
index 7e1ec5c2cb1195864e6e812072b13f7a540ad4e6..29306663c237c2c8ea2df01586c5fe840ca4a4e3 100644
--- a/base/task_scheduler/scheduler_thread_pool_unittest.cc
+++ b/base/task_scheduler/scheduler_thread_pool_unittest.cc
@@ -25,6 +25,7 @@
 #include "base/task_scheduler/task_tracker.h"
 #include "base/threading/platform_thread.h"
 #include "base/threading/simple_thread.h"
+#include "base/threading/thread_checker_impl.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
@@ -79,7 +80,11 @@ class TaskFactory {
       : cv_(&lock_),
         task_runner_(thread_pool->CreateTaskRunnerWithTraits(TaskTraits(),
                                                              execution_mode)),
-        execution_mode_(execution_mode) {}
+        execution_mode_(execution_mode) {
+    // Detach |thread_checker_| from the current thread. It will be attached to
+    // the first thread that calls ThreadCheckerImpl::CalledOnValidThread().
+    thread_checker_.DetachFromThread();
+  }
 
   // Posts a task through |task_runner_|. If |post_nested_task| is true, the
   // task will post a new task when it runs. If |event| is set, the task will
@@ -119,11 +124,15 @@ class TaskFactory {
     {
       AutoLock auto_lock(lock_);
 
-      if (execution_mode_ == ExecutionMode::SEQUENCED &&
+      if ((execution_mode_ == ExecutionMode::SEQUENCED ||
+           execution_mode_ == ExecutionMode::SINGLE_THREADED) &&
           task_index != ran_tasks_.size()) {
-        ADD_FAILURE() << "A SEQUENCED task didn't run in the expected order.";
+        ADD_FAILURE() << "A task didn't run in the expected order.";
       }
 
+      if (execution_mode_ == ExecutionMode::SINGLE_THREADED)
+        EXPECT_TRUE(thread_checker_.CalledOnValidThread());
+
       if (ran_tasks_.find(task_index) != ran_tasks_.end())
         ADD_FAILURE() << "A task ran more than once.";
       ran_tasks_.insert(task_index);
@@ -153,6 +162,10 @@ class TaskFactory {
   // Indexes of tasks that ran.
   std::unordered_set<size_t> ran_tasks_;
 
+  // Used to verify that all tasks run on the same thread when |execution_mode_|
+  // is SINGLE_THREADED.
+  ThreadCheckerImpl thread_checker_;
+
   DISALLOW_COPY_AND_ASSIGN(TaskFactory);
 };
 
@@ -277,8 +290,8 @@ TEST_P(TaskSchedulerThreadPoolTest, NestedPostTasks) {
 
 TEST_P(TaskSchedulerThreadPoolTest, PostTasksWithOneAvailableThread) {
   // Post tasks to keep all threads busy except one until |event| is signaled.
-  // Use different factories so that tasks are added to different sequences and
-  // can run simultaneously when the execution mode is SEQUENCED.
+  // Use different factories so that tasks are assigned to different sequences
+  // or threads when the execution mode is SEQUENCED or SINGLE_THREADED.
   WaitableEvent event(true, false);
   std::vector<std::unique_ptr<TaskFactory>> blocked_task_factories;
   for (size_t i = 0; i < (kNumThreadsInThreadPool - 1); ++i) {
@@ -306,8 +319,8 @@ TEST_P(TaskSchedulerThreadPoolTest, PostTasksWithOneAvailableThread) {
 TEST_P(TaskSchedulerThreadPoolTest, Saturate) {
   // Verify that it is possible to have |kNumThreadsInThreadPool|
   // tasks/sequences running simultaneously. Use different factories so that
-  // tasks are added to different sequences and can run simultaneously when the
-  // execution mode is SEQUENCED.
+  // tasks are assigned to different sequences or threads when the execution
+  // mode is SEQUENCED or SINGLE_THREADED.
   WaitableEvent event(true, false);
   std::vector<std::unique_ptr<TaskFactory>> factories;
   for (size_t i = 0; i < kNumThreadsInThreadPool; ++i) {
@@ -331,6 +344,9 @@ INSTANTIATE_TEST_CASE_P(Parallel,
 INSTANTIATE_TEST_CASE_P(Sequenced,
                         TaskSchedulerThreadPoolTest,
                         ::testing::Values(ExecutionMode::SEQUENCED));
+INSTANTIATE_TEST_CASE_P(SingleThreaded,
+                        TaskSchedulerThreadPoolTest,
+                        ::testing::Values(ExecutionMode::SINGLE_THREADED));
 
 }  // namespace
 }  // namespace internal