Chromium implementation of discardBackbuffer WebGraphicsContext3D extension.

content/common/gpu/texture_image_transport_surface.cc

 // Copyright (c) 2012 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 "content/common/gpu/texture_image_transport_surface.h"
 
 #include "content/common/gpu/gpu_channel.h"
 #include "content/common/gpu/gpu_channel_manager.h"
 #include "content/common/gpu/gpu_messages.h"
 #include "gpu/command_buffer/service/context_group.h"
@@ skipping 139 matching lines @@
 void TextureImageTransportSurface::SetBufferAllocation(
     BufferAllocationState state) {
   if (!helper_->MakeCurrent())
     return;
   switch (state) {
     case BUFFER_ALLOCATION_FRONT_AND_BACK:
       CreateBackTexture(textures_[back()].size);
       break;
     case BUFFER_ALLOCATION_FRONT_ONLY:
     case BUFFER_ALLOCATION_NONE:
-      // TODO(piman): Re-enable this (or something else) when we fix the
-      // renderer so it doesn't try to draw/swap on deleted back buffers.
-      // ReleaseBackTexture();
+      ReleaseBackTexture();
       break;
   };
 }
 
 void* TextureImageTransportSurface::GetShareHandle() {
   return GetHandle();
 }
 
 void* TextureImageTransportSurface::GetDisplay() {
   return parent_stub_.get() ? parent_stub_->surface()->GetDisplay() : NULL;
@@ skipping 15 matching lines @@
 
   stub->RemoveDestructionObserver(this);
   stub_destroyed_ = true;
 }
 
 bool TextureImageTransportSurface::SwapBuffers() {
   glFlush();
   front_ = back();
   previous_damage_rect_ = gfx::Rect(textures_[front_].size);
 
+  DCHECK(textures_[front_].client_id != 0);
+
   GpuHostMsg_AcceleratedSurfaceBuffersSwapped_Params params;
   params.surface_handle = textures_[front_].client_id;
   helper_->SendAcceleratedSurfaceBuffersSwapped(params);
   helper_->SetScheduled(false);
   return true;
 }
 
 bool TextureImageTransportSurface::PostSubBuffer(
     int x, int y, int width, int height) {
   if (!parent_stub_.get())
@@ skipping 198 matching lines @@
 #endif
 }
 
 TextureInfo* TextureImageTransportSurface::GetParentInfo(uint32 client_id) {
   DCHECK(parent_stub_.get());
   TextureManager* texture_manager =
       parent_stub_->decoder()->GetContextGroup()->texture_manager();
   TextureInfo* info = texture_manager->GetTextureInfo(client_id);
   return info;
 }