Send a message through the ozone channel to recreate buffers

ui/ozone/platform/drm/host/drm_window_host.h

Index: ui/ozone/platform/drm/host/drm_window_host.h
diff --git a/ui/ozone/platform/drm/host/drm_window_host.h b/ui/ozone/platform/drm/host/drm_window_host.h
index 74021f816212e42b2bc29cd4d84f0165d04c049f..709dea4ce7ef3691aaa68aab7fc81f46b7d41491 100644
--- a/ui/ozone/platform/drm/host/drm_window_host.h
+++ b/ui/ozone/platform/drm/host/drm_window_host.h
@@ -11,6 +11,7 @@
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/ozone/platform/drm/host/channel_observer.h"
+#include "ui/ozone/public/gpu_platform_support_host.h"
 #include "ui/platform_window/platform_window.h"
 
 namespace ui {
@@ -34,7 +35,8 @@ class EventFactoryEvdev;
 // associated with the window (the surface is created on the GPU process).
 class DrmWindowHost : public PlatformWindow,
                       public PlatformEventDispatcher,
-                      public ChannelObserver {
+                      public ChannelObserver,
+                      public GpuPlatformSupportHost {
  public:
   DrmWindowHost(PlatformWindowDelegate* delegate,
                 const gfx::Rect& bounds,
@@ -75,6 +77,16 @@ class DrmWindowHost : public PlatformWindow,
   void OnChannelEstablished() override;
   void OnChannelDestroyed() override;
 
+  // GpuPlatformSupportHost:
+  void OnChannelEstablished(
+      int host_id,
+      scoped_refptr<base::SingleThreadTaskRunner> send_runner,
+      const base::Callback<void(IPC::Message*)>& send_callback) override;
+  void OnChannelDestroyed(int host_id) override;
+  bool OnMessageReceived(const IPC::Message& message) override;
+
+  void OnWindowMappingChanged(gfx::AcceleratedWidget widget);
+
  private:
   void SendBoundsChange();