[TaskScheduler] Temporarily co-init all TaskScheduler threads to match SequencedWorkerPool's behavi…

base/task_scheduler/scheduler_worker.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/task_scheduler/scheduler_worker.h"
 
 #include <stddef.h>
 
 #include <memory>
 #include <utility>
 
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "base/task_scheduler/task_tracker.h"
 #include "build/build_config.h"
 
 #if defined(OS_MACOSX)
 #include "base/mac/scoped_nsautorelease_pool.h"
+#elif defined(OS_WIN)
+#include "base/win/scoped_com_initializer.h"
 #endif
 
 namespace base {
 namespace internal {
 
 class SchedulerWorker::Thread : public PlatformThread::Delegate {
  public:
   ~Thread() override = default;
 
   static std::unique_ptr<Thread> Create(SchedulerWorker* outer) {
@@ skipping 10 matching lines @@
     std::unique_ptr<Thread> detached_thread;
 
     outer_->delegate_->OnMainEntry(
         outer_, outer_->last_detach_time_.is_null()
                     ? TimeDelta::Max()
                     : TimeTicks::Now() - outer_->last_detach_time_);
 
     // A SchedulerWorker starts out waiting for work.
     WaitForWork();
 
+#if defined(OS_WIN)
+    // This is required as SequencedWorkerPool previously blindly CoInitialized
+    // all of its threads.
+    // TODO: Get rid of this broad COM scope and force tasks that care about a
+    // CoInitialized environment to request one (via an upcoming ExecutionMode).
+    win::ScopedCOMInitializer com_initializer;
+#endif
+
     while (!outer_->task_tracker_->IsShutdownComplete() &&
            !outer_->should_exit_for_testing_.IsSet()) {
       DCHECK(outer_);
 
 #if defined(OS_MACOSX)
       mac::ScopedNSAutoreleasePool autorelease_pool;
 #endif
 
       UpdateThreadPriority(GetDesiredThreadPriority());
 
@@ skipping 209 matching lines @@
   thread_ = Thread::Create(this);
 }
 
 void SchedulerWorker::CreateThreadAssertSynchronized() {
   thread_lock_.AssertAcquired();
   CreateThread();
 }
 
 }  // namespace internal
 }  // namespace base