Switch DRM platform to using a separate thread

ui/ozone/platform/drm/gpu/drm_device_manager.cc

 // Copyright 2015 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 "ui/ozone/platform/drm/gpu/drm_device_manager.h"
 
 #include "base/file_descriptor_posix.h"
 #include "base/single_thread_task_runner.h"
 #include "ui/ozone/platform/drm/gpu/drm_device.h"
 #include "ui/ozone/platform/drm/gpu/drm_device_generator.h"
@@ skipping 37 matching lines @@
     return false;
   }
 
   scoped_refptr<DrmDevice> device =
       drm_device_generator_->CreateDevice(path, file.Pass());
   if (!device) {
     LOG(ERROR) << "Could not initialize DRM device for " << path.value();
     return false;
   }
 
-  if (io_task_runner_)
-    device->InitializeTaskRunner(io_task_runner_);
-
   if (!primary_device_)
     primary_device_ = device;
 
   devices_.push_back(device);
   return true;
 }
 
 void DrmDeviceManager::RemoveDrmDevice(const base::FilePath& path) {
   DCHECK(thread_checker_.CalledOnValidThread());
   auto it =
       std::find_if(devices_.begin(), devices_.end(), FindByDevicePath(path));
   if (it == devices_.end()) {
     VLOG(2) << "Got request to remove non-existent device: " << path.value();
     return;
   }
 
   DCHECK_NE(primary_device_, *it);
   devices_.erase(it);
 }
 
-void DrmDeviceManager::InitializeIOTaskRunner(
-    const scoped_refptr<base::SingleThreadTaskRunner>& task_runner) {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  DCHECK(!io_task_runner_);
-  io_task_runner_ = task_runner;
-  for (const auto& device : devices_)
-    device->InitializeTaskRunner(io_task_runner_);
-}
-
 void DrmDeviceManager::UpdateDrmDevice(gfx::AcceleratedWidget widget,
                                        const scoped_refptr<DrmDevice>& device) {
   base::AutoLock lock(lock_);
   drm_device_map_[widget] = device;
 }
 
 void DrmDeviceManager::RemoveDrmDevice(gfx::AcceleratedWidget widget) {
   base::AutoLock lock(lock_);
   auto it = drm_device_map_.find(widget);
   if (it != drm_device_map_.end())
@@ skipping 17 matching lines @@
 
   return it->second;
 }
 
 const DrmDeviceVector& DrmDeviceManager::GetDrmDevices() const {
   DCHECK(thread_checker_.CalledOnValidThread());
   return devices_;
 }
 
 }  // namespace ui