Run ScopedTaskScheduler tasks synchronously.

content/public/test/test_browser_thread_bundle.cc

Index: content/public/test/test_browser_thread_bundle.cc
diff --git a/content/public/test/test_browser_thread_bundle.cc b/content/public/test/test_browser_thread_bundle.cc
index 537e24534c3bda496b4648d0c31e12738d2f2974..ca2d57b18a3011e604c825036986aafc8f36f1c0 100644
--- a/content/public/test/test_browser_thread_bundle.cc
+++ b/content/public/test/test_browser_thread_bundle.cc
@@ -4,8 +4,10 @@
 
 #include "content/public/test/test_browser_thread_bundle.h"
 
+#include "base/memory/ptr_util.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
+#include "base/test/scoped_task_scheduler.h"
 #include "content/browser/browser_thread_impl.h"
 #include "content/public/test/test_browser_thread.h"
 
@@ -58,41 +60,39 @@ void TestBrowserThreadBundle::Init() {
   // There must be a thread to start to use DONT_START_THREADS
   CHECK((options_ & ~IO_MAINLOOP) != DONT_START_THREADS);
 
-  if (options_ & IO_MAINLOOP) {
-    message_loop_.reset(new base::MessageLoopForIO());

[gab, 2016/12/08 20:15:45]

I prefered that the loop be owned by TestBrowserThreadBundle. Can
ScopedTaskScheduler take an optional externally provided MessageLoop (like
base::Thread)?

Also avoids adding MessageLoop::current() calls below.

[fdoray, 2016/12/09 16:26:42]

Done.

-  } else {
-    message_loop_.reset(new base::MessageLoopForUI());
-  }
+  task_scheduler_ = base::MakeUnique<base::test::ScopedTaskScheduler>(
+      options_ & IO_MAINLOOP ? base::test::ScopedTaskScheduler::DEFAULT
+                             : base::test::ScopedTaskScheduler::UI_MAIN_LOOP);

[gab, 2016/12/08 20:15:45]

So if using a REAL_IO_THREAD, it's not possible to have a TaskScheduler than can
do async I/O?

I think we should have a REAL_TASK_SCHEDULER option that would create a simple
task scheduler without a MessageLoop.

[fdoray, 2016/12/09 16:26:42]

n/a See
https://codereview.chromium.org/2557083002/diff/40001/base/test/scoped_task_s...

[gab, 2016/12/09 20:04:17]

But we might still want a REAL_TASK_SCHEDULER? Would mean we'd keep
TaskScheduler::FlushForTesting() too I guess which could be confusing when the
MessageLoop based one is around... guess not then... just thinking out loud here
:)

[fdoray, 2016/12/12 18:18:50]

I would wait until we have a real use case before adding the REAL_TASK_SCHEDULER
option. Unless tasks synchronously wait for other tasks to run (which is bad),
this option should not be needed.

 
   ui_thread_.reset(
-      new TestBrowserThread(BrowserThread::UI, message_loop_.get()));
+      new TestBrowserThread(BrowserThread::UI, base::MessageLoop::current()));
 
   if (options_ & REAL_DB_THREAD) {
     db_thread_.reset(new TestBrowserThread(BrowserThread::DB));
   } else {
     db_thread_.reset(
-        new TestBrowserThread(BrowserThread::DB, message_loop_.get()));
+        new TestBrowserThread(BrowserThread::DB, base::MessageLoop::current()));
   }
 
   if (options_ & REAL_FILE_THREAD) {
     file_thread_.reset(new TestBrowserThread(BrowserThread::FILE));
   } else {
-    file_thread_.reset(
-        new TestBrowserThread(BrowserThread::FILE, message_loop_.get()));
+    file_thread_.reset(new TestBrowserThread(BrowserThread::FILE,
+                                             base::MessageLoop::current()));
   }
 
   file_user_blocking_thread_.reset(new TestBrowserThread(
-      BrowserThread::FILE_USER_BLOCKING, message_loop_.get()));
+      BrowserThread::FILE_USER_BLOCKING, base::MessageLoop::current()));
   process_launcher_thread_.reset(new TestBrowserThread(
-      BrowserThread::PROCESS_LAUNCHER, message_loop_.get()));
-  cache_thread_.reset(
-      new TestBrowserThread(BrowserThread::CACHE, message_loop_.get()));
+      BrowserThread::PROCESS_LAUNCHER, base::MessageLoop::current()));
+  cache_thread_.reset(new TestBrowserThread(BrowserThread::CACHE,
+                                            base::MessageLoop::current()));
 
   if (options_ & REAL_IO_THREAD) {
     io_thread_.reset(new TestBrowserThread(BrowserThread::IO));
   } else {
     io_thread_.reset(
-        new TestBrowserThread(BrowserThread::IO, message_loop_.get()));
+        new TestBrowserThread(BrowserThread::IO, base::MessageLoop::current()));
   }
 
   if (!(options_ & DONT_START_THREADS))