ozone: gbm: Add overlay support

ui/ozone/platform/dri/gbm_surface.cc

 // Copyright 2014 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/dri/gbm_surface.h"
 
 #include <gbm.h>
 
 #include "base/logging.h"
 #include "third_party/skia/include/core/SkImageInfo.h"
@@ skipping 63 matching lines @@
 
   BufferData* data = BufferData::GetData(buffers_[front_buffer_ ^ 1]);
   CHECK(data);
   return data->handle();
 }
 
 gfx::Size GbmSurface::Size() const {
   return size_;
 }
 
-void GbmSurface::SwapBuffers() {
-  // If there was a frontbuffer, is no longer active. Release it back to GBM.
-  if (buffers_[front_buffer_])
-    gbm_surface_release_buffer(native_surface_, buffers_[front_buffer_]);
-
-  // Update the index to the frontbuffer.
-  front_buffer_ ^= 1;
-  // We've just released it. Since GBM doesn't guarantee we'll get the same
-  // buffer back, we set it to NULL so we don't keep track of objects that may
-  // have been destroyed.
-  buffers_[front_buffer_ ^ 1] = NULL;
-}
-
-void GbmSurface::LockCurrentDrawable() {
+// Before scheduling the backbuffer to be scanned out we need to "lock" it.
+// When we lock it, GBM will give a pointer to a buffer representing the
+// backbuffer. It will also update its information on which buffers can not be
+// used for drawing. The buffer will be released when the page flip event
+// occurs (see SwapBuffers). This is called from HardwareDisplayController
+// before scheduling a page flip.
+void GbmSurface::PreSwapBuffers() {
   CHECK(native_surface_);
   // Lock the buffer we want to display.
   buffers_[front_buffer_ ^ 1] = gbm_surface_lock_front_buffer(native_surface_);
 
   BufferData* data = BufferData::GetData(buffers_[front_buffer_ ^ 1]);
   // If it is a new buffer, it won't have any data associated with it. So we
   // create it. On creation it will associate itself with the buffer and
   // register the buffer.
   if (!data) {
     data = BufferData::CreateData(dri_, buffers_[front_buffer_ ^ 1]);
     DCHECK(data) << "Failed to associate the buffer with the controller";
   }
 }
 
+void GbmSurface::SwapBuffers() {
+  // If there was a frontbuffer, is no longer active. Release it back to GBM.
+  if (buffers_[front_buffer_])
+    gbm_surface_release_buffer(native_surface_, buffers_[front_buffer_]);
+
+  // Update the index to the frontbuffer.
+  front_buffer_ ^= 1;
+  // We've just released it. Since GBM doesn't guarantee we'll get the same
+  // buffer back, we set it to NULL so we don't keep track of objects that may
+  // have been destroyed.
+  buffers_[front_buffer_ ^ 1] = NULL;
+}
+
 }  // namespace ui