Switch DRM platform to using a separate thread

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

Index: ui/ozone/platform/drm/gpu/drm_vsync_provider.h
diff --git a/ui/ozone/platform/drm/gpu/drm_vsync_provider.h b/ui/ozone/platform/drm/gpu/drm_vsync_provider.h
index db51f1bde141a17b08b0ad9bd69d89732519ca3a..95a8485012046fabe7e67113375ac85f94a2b86a 100644
--- a/ui/ozone/platform/drm/gpu/drm_vsync_provider.h
+++ b/ui/ozone/platform/drm/gpu/drm_vsync_provider.h
@@ -5,21 +5,30 @@
 #ifndef UI_OZONE_PLATFORM_IMPL_DRM_VSYNC_PROVIDER_H_
 #define UI_OZONE_PLATFORM_IMPL_DRM_VSYNC_PROVIDER_H_
 
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
 #include "ui/gfx/vsync_provider.h"
 
+namespace base {
+class SingleThreadTaskRunner;
+}
+
 namespace ui {
 
 class DrmWindow;
 
 class DrmVSyncProvider : public gfx::VSyncProvider {
  public:
-  DrmVSyncProvider(DrmWindow* window);
+  DrmVSyncProvider(
+      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
+      base::WeakPtr<DrmWindow> window);
   ~DrmVSyncProvider() override;
 
   void GetVSyncParameters(const UpdateVSyncCallback& callback) override;
 
  private:
-  DrmWindow* window_;  // Not owned.
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+  base::WeakPtr<DrmWindow> window_;
 
   DISALLOW_COPY_AND_ASSIGN(DrmVSyncProvider);
 };