gpu: Implement idle async pixel transfers.

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index ced015f1593d1297b40e30c995f87a28b86796ec..d4d85be5a764564565498ab7c83a53262242b71e 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -573,6 +573,8 @@ class GLES2DecoderImpl : public GLES2Decoder {
     return vertex_array_manager_.get();
   }
   virtual bool ProcessPendingQueries() OVERRIDE;
+  virtual bool HasMoreWork() OVERRIDE;
+  virtual bool PerformIdleWork() OVERRIDE;
 
   virtual void SetResizeCallback(
       const base::Callback<void(gfx::Size)>& callback) OVERRIDE;
@@ -9115,6 +9117,19 @@ bool GLES2DecoderImpl::ProcessPendingQueries() {
   return query_manager_->HavePendingQueries();
 }
 
+bool GLES2DecoderImpl::HasMoreWork() {
+  return ProcessPendingQueries() ||
+      async_pixel_transfer_delegate_->CanProcessPendingTransfers();
+}
+
+bool GLES2DecoderImpl::PerformIdleWork() {
+  if (!async_pixel_transfer_delegate_->CanProcessPendingTransfers())
+    return false;
+  async_pixel_transfer_delegate_->ProcessPendingTransfers();
+  RestoreCurrentTexture2DBindings();

[greggman, 2013/03/08 21:06:21]

What do think about moving RestoreCurrentTexture2DBindings inside
ProcessPendingTransfers?

I've made all the state restore functions public from GLES2Decoder so you can
pass 'this' into ProcessPendingTransfers.

In this particular case you really want to call

decoder->RestoreTextureUnitBindings(0);
decoder->RestoreActiveTexture();

The advantage is ProcessPendingTransfers can clean up after itself. The caller
doesn't need to know what happens inside like it does here.

I did this for DoCopyTextureCHROMIUM recently.
see http://goo.gl/XfXlE

[reveman, 2013/03/12 00:31:42]

Makes sense. The latest patch calls ProcessFinishedAsyncTransfers() here instead
as that's more appropriate. ProcessFinishedAsyncTransfers() calls
RestoreCurrentTexture2DBindings() and we probably want to clean that up as you
described but I would prefer to do that in a follow up patch. Latest patch at
least doesn't make things worse.

+  return async_pixel_transfer_delegate_->CanProcessPendingTransfers();
+}
+
 error::Error GLES2DecoderImpl::HandleBeginQueryEXT(
     uint32 immediate_data_size, const cmds::BeginQueryEXT& c) {
   GLenum target = static_cast<GLenum>(c.target);