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 1d642fd1d16cc08c26481deb1f9100971493ddb9..ba7cac8060db2f2c66eade46afccab75b383a1bb 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -627,6 +627,8 @@ class GLES2DecoderImpl : public GLES2Decoder {
     return vertex_array_manager_.get();
   }
   virtual bool ProcessPendingQueries() OVERRIDE;
+  virtual bool HasMoreIdleWork() OVERRIDE;
+  virtual void PerformIdleWork() OVERRIDE;
 
   virtual void SetResizeCallback(
       const base::Callback<void(gfx::Size)>& callback) OVERRIDE;
@@ -9245,6 +9247,18 @@ bool GLES2DecoderImpl::ProcessPendingQueries() {
   return query_manager_->HavePendingQueries();
 }
 
+bool GLES2DecoderImpl::HasMoreIdleWork() {
+  return async_pixel_transfer_delegate_->NeedsProcessMorePendingTransfers();
+}
+
+void GLES2DecoderImpl::PerformIdleWork() {
+  if (!async_pixel_transfer_delegate_->NeedsProcessMorePendingTransfers())
+    return;
+  if (async_pixel_transfer_delegate_->ProcessMorePendingTransfers())

[greggman, 2013/03/14 18:15:46]

I think I asked this in another CL. Would it be better to pass 'this' to
ProcessModePendingTransfers so that ProcessMorePendingTransfers can restore its
own state? It seems strange that the code out here has to know what state to
restore.

Also, you either need to remove the calls to glActiveTexture in
async_pixel_transfer_delegate_idle.cc or else you need to call
RestoreTextureUnitBindings(0)

[epenner, 2013/03/14 18:23:24]

It's currently a layering violation to do that, but we could make a
"RestoreCurrentTexture2DBindings" closure or interface that could be called. I
suggested we keep the booleans before since it's just a few functions, but it's
your call.

If the code moved the layering violation would go away, but I kind of like how
it currently has no dependency on the decoder.

[reveman, 2013/03/14 19:21:47]

Oh sorry, so we've gone back and forth here without me noticing. I switch to
just using the existing ProcessFinishedAsyncTransfers() call here based on your
feedback but epenner pointed out that this was a bit fragile so now we're back
to using a bool return value again.

I'd prefer to keep the current bool return value for now
(BindCompletedAsyncTransfers already does this) and clean it up be removing this
behavior from the AsyncPixelTransferDelegate completely in a follow up patch.
I've added TODO comments to the code and filed crbug.com/196303. gman, you OK
with that?
Done. Thanks for noticing this.

+    RestoreCurrentTexture2DBindings();
+  ProcessFinishedAsyncTransfers();
+}
+
 error::Error GLES2DecoderImpl::HandleBeginQueryEXT(
     uint32 immediate_data_size, const cmds::BeginQueryEXT& c) {
   GLenum target = static_cast<GLenum>(c.target);