gpu: Add the ability to wait on upload completion.

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 288d7c98d2da4518d47bed697b79757e2db13dea..c8cafa7884d177961dc112045e3380e0bf565ffe 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -10157,6 +10157,26 @@ error::Error GLES2DecoderImpl::HandleAsyncTexSubImage2DCHROMIUM(
   return error::kNoError;
 }
 
+error::Error GLES2DecoderImpl::HandleWaitAsyncTexImage2DCHROMIUM(
+    uint32 immediate_data_size, const cmds::WaitAsyncTexImage2DCHROMIUM& c) {
+  TRACE_EVENT0("gpu", "GLES2DecoderImpl::HandleWaitAsyncTexImage2DCHROMIUM");
+  GLenum target = static_cast<GLenum>(c.target);
+
+  if (GL_TEXTURE_2D != target) {
+    SetGLError(GL_INVALID_ENUM, "glWaitAsyncTexImage2DCHROMIUM", "target");
+    return error::kNoError;
+  }
+  Texture* info = GetTextureInfoForTarget(target);
+  if (!info) {
+      SetGLError(GL_INVALID_OPERATION,
+                 "glWaitAsyncTexImage2DCHROMIUM", "unknown texture");
+    return error::kNoError;
+  }
+  async_pixel_transfer_delegate_->WaitForTransferCompletion(

[greggman, 2013/03/04 21:25:53]

Are you sure you want to wait here vs checking if it's okay to proceed and
returning error::kDeferCommandUntilLater if it's not. As it is this will block
the GPU process where as error::kDeferCommandUntilLater will let the GPU process
process other command buffers.

[Sami, 2013/03/05 12:25:26]

Yeah, we talked about doing this but shied away for now since we weren't exactly
sure how to make this avoid blocking other contexts. I guess the problem with
kDeferCommandUntilLater is that if there aren't any pending commands the GPU
thread will busy-loop on this same command, right? I can experiment with this
and do a follow-up patch if I find a way to do without blocking everyone.

FWIW, in my tests this call ends up blocking only very rarely, because the
uploads generally finish sooner than we end up needing them. The benefit is that
we can submit the rendering commands sooner and avoid a bubble in the pipeline.

+      info->GetAsyncTransferState());
+  return error::kNoError;
+}
+
 // Include the auto-generated part of this file. We split this because it means
 // we can easily edit the non-auto generated parts right here in this file
 // instead of having to edit some template or the code generator.