[content test_utils] Fix RunAllPendingInMessageLoop(BrowserThread::IO) under REAL_IO_THREAD

See bug for details.

Bug: 1035604
Change-Id: I071fce979094d291171a7fba4b90da2bf70ce711
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1974585Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Carlos Caballero <carlscab@google.com>
Commit-Queue: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#726416}

content/browser/scheduler/browser_task_executor.cc

@@ -246,8 +246,8 @@ void BrowserTaskExecutor::ResetForTesting() {
 // static
 void BrowserTaskExecutor::PostFeatureListSetup() {
   DCHECK(g_browser_task_executor);
-  DCHECK(g_browser_task_executor->ui_thread_executor_);
-  DCHECK(g_browser_task_executor->io_thread_executor_);
+  DCHECK(g_browser_task_executor->browser_ui_thread_handle_);
+  DCHECK(g_browser_task_executor->browser_io_thread_handle_);
   g_browser_task_executor->browser_ui_thread_handle_
       ->PostFeatureListInitializationSetup();
   g_browser_task_executor->browser_io_thread_handle_
@@ -285,12 +285,6 @@ void BrowserTaskExecutor::RunAllPendingTasksOnThreadForTesting(
           ->ScheduleRunAllPendingTasksForTesting(run_loop.QuitClosure());
       break;
     case BrowserThread::IO: {
-      // In tests there may not be a functional IO thread.
-      if (!g_browser_task_executor->io_thread_executor_ ||
-          !g_browser_task_executor->io_thread_executor_
-               ->HasDelegateForTesting()) {
-        return;
-      }
       g_browser_task_executor->browser_io_thread_handle_
           ->ScheduleRunAllPendingTasksForTesting(run_loop.QuitClosure());
       break;

content/browser/scheduler/browser_task_executor.h

@@ -230,8 +230,6 @@ class CONTENT_EXPORT BrowserTaskExecutor : public BaseBrowserTaskExecutor {
       return std::move(browser_io_thread_delegate_);
     }
 
-    bool HasDelegateForTesting() const { return !!browser_io_thread_delegate_; }
-
    private:
     BrowserThread::ID GetCurrentThreadID() const override;
 

content/public/test/test_utils_unittest.cc

@@ -9,6 +9,9 @@
 #include "base/test/bind_test_util.h"
 #include "base/test/task_environment.h"
 #include "base/threading/platform_thread.h"
+#include "content/public/browser/browser_task_traits.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/test/browser_task_environment.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 // Regression test for crbug.com/1035189.
@@ -18,7 +21,7 @@ TEST(ContentTestUtils, NestedRunAllTasksUntilIdleWithPendingThreadPoolWork) {
   bool thread_pool_task_completed = false;
   base::PostTask(
       FROM_HERE, {base::ThreadPool()}, base::BindLambdaForTesting([&]() {
-        base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(200));
+        base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(100));
         thread_pool_task_completed = true;
       }));
 
@@ -35,3 +38,94 @@ TEST(ContentTestUtils, NestedRunAllTasksUntilIdleWithPendingThreadPoolWork) {
   run_loop.Run();
   EXPECT_TRUE(thread_pool_task_completed);
 }
+
+// Regression test for crbug.com/1035604.
+TEST(ContentTestUtils, FlushRealIOThread) {
+  content::BrowserTaskEnvironment task_environment{
+      content::BrowserTaskEnvironment::REAL_IO_THREAD};
+
+  bool io_task_completed = false;
+  base::PostTask(
+      FROM_HERE, {content::BrowserThread::IO},
+      base::BindLambdaForTesting([&]() {
+        base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(100));
+        io_task_completed = true;
+      }));
+
+  content::RunAllPendingInMessageLoop(content::BrowserThread::IO);
+  EXPECT_TRUE(io_task_completed);
+}
+
+TEST(ContentTestUtils, NestedFlushRealIOThread) {
+  content::BrowserTaskEnvironment task_environment{
+      content::BrowserTaskEnvironment::REAL_IO_THREAD};
+
+  bool io_task_completed = false;
+  base::PostTask(
+      FROM_HERE, {content::BrowserThread::IO},
+      base::BindLambdaForTesting([&]() {
+        base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(100));
+        io_task_completed = true;
+      }));
+
+  base::RunLoop run_loop;
+
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE, base::BindLambdaForTesting([&]() {
+        content::RunAllPendingInMessageLoop(content::BrowserThread::IO);
+        EXPECT_TRUE(io_task_completed);
+        run_loop.Quit();
+      }));
+
+  run_loop.Run();
+  EXPECT_TRUE(io_task_completed);
+}
+
+TEST(ContentTestUtils, FlushRealIOThreadWithPendingBestEffortTask) {
+  content::BrowserTaskEnvironment task_environment{
+      content::BrowserTaskEnvironment::REAL_IO_THREAD};
+
+  bool io_task_completed = false;
+  base::PostTask(
+      FROM_HERE, {content::BrowserThread::IO, base::TaskPriority::BEST_EFFORT},
+      base::BindLambdaForTesting([&]() {
+        base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(100));
+        io_task_completed = true;
+      }));
+
+  content::RunAllPendingInMessageLoop(content::BrowserThread::IO);
+  EXPECT_TRUE(io_task_completed);
+}
+
+// Same as FlushRealIOThreadWithPendingBestEffortTask but when BrowserThread::IO
+// is multiplexed with BrowserThread::UI on the main thread (i.e. the default
+// under BrowserTaskEnvironment).
+TEST(ContentTestUtils, FlushFakeIOThread) {
+  content::BrowserTaskEnvironment task_environment;
+
+  bool io_task_completed = false;
+  base::PostTask(
+      FROM_HERE, {content::BrowserThread::IO, base::TaskPriority::BEST_EFFORT},
+      base::BindLambdaForTesting([&]() {
+        base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(100));
+        io_task_completed = true;
+      }));
+
+  content::RunAllPendingInMessageLoop(content::BrowserThread::IO);
+  EXPECT_TRUE(io_task_completed);
+}
+
+TEST(ContentTestUtils, FlushUIThread) {
+  content::BrowserTaskEnvironment task_environment;
+
+  bool ui_task_completed = false;
+  base::PostTask(
+      FROM_HERE, {content::BrowserThread::UI, base::TaskPriority::BEST_EFFORT},
+      base::BindLambdaForTesting([&]() {
+        base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(100));
+        ui_task_completed = true;
+      }));
+
+  content::RunAllPendingInMessageLoop(content::BrowserThread::UI);
+  EXPECT_TRUE(ui_task_completed);
+}