Switch DRM platform to using a separate thread

ui/ozone/platform/drm/gpu/drm_thread.h

+// 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.
+
+#ifndef UI_OZONE_PLATFORM_DRM_GPU_DRM_THREAD_H_
+#define UI_OZONE_PLATFORM_DRM_GPU_DRM_THREAD_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "base/threading/thread.h"
+#include "ui/gfx/native_widget_types.h"
+
+namespace ui {
+
+class DrmDeviceManager;
+class DrmGpuPlatformSupport;
+class DrmGpuPlatformSupportProxy;
+class DrmWindow;
+class ScanoutBufferGenerator;
+class ScreenManager;
+
+// Holds all the DRM related state and performs all DRM related operations with
+// the exception of buffer allocations which happen on the threads requiring the
+// allocations.
+//
+// The DRM thread is used to insulate DRM operations from potential blocking
+// behaviour on the GPU main thread in order to reduce the potential for jank
+// (for example jank in the cursor if the GPU main thread is performing heavy
+// operations). The inverse is also true as blocking operations on the DRM
+// thread (such as modesetting) no longer block the GPU main thread.
+class DrmThread : public base::Thread {
+ public:
+  DrmThread();
+  ~DrmThread() override;
+
+  void Start();
+
+  // Safe to use from any thread. Access to the device manager is direct since
+  // the device manager performs its own locking since buffer allocations need
+  // to happen on the main GPU thread and on the IO GPU thread without waiting.
+  DrmDeviceManager* device_manager() const { return device_manager_.get(); }
+
+  // Safe to use from any thread.
+  base::WeakPtr<DrmGpuPlatformSupport> GetGpuPlatformSupport() const;
+
+  // Safe to use from any thread.
+  base::WeakPtr<DrmWindow> GetWindow(gfx::AcceleratedWidget widget) const;
+
+  // base::Thread:
+  void Init() override;
+
+ protected:
+  scoped_ptr<DrmDeviceManager> device_manager_;
+  scoped_ptr<ScanoutBufferGenerator> buffer_generator_;
+  scoped_ptr<ScreenManager> screen_manager_;
+  scoped_ptr<DrmGpuPlatformSupport> gpu_platform_support_;
+
+ private:
+  void GetGpuPlatformSupportOnThread(
+      base::WeakPtr<DrmGpuPlatformSupport>* support) const;
+
+  void GetWindowOnThread(gfx::AcceleratedWidget widget,
+                         base::WeakPtr<DrmWindow>* weak_window) const;
+
+  DISALLOW_COPY_AND_ASSIGN(DrmThread);
+};
+
+}  // namespace ui
+
+#endif  // UI_OZONE_PLATFORM_DRM_GPU_DRM_THREAD_H_