gpu: Add a new extension CHROMIUM_deschedule.

gpu/command_buffer/service/gles2_cmd_decoder_autogen.h

Index: gpu/command_buffer/service/gles2_cmd_decoder_autogen.h
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder_autogen.h b/gpu/command_buffer/service/gles2_cmd_decoder_autogen.h
index 52b7fd6988891b2402e5fe58722070c53eac3acc..af547ee64814f7b190ec35bdad4f4fb844117c5e 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder_autogen.h
+++ b/gpu/command_buffer/service/gles2_cmd_decoder_autogen.h
@@ -4673,6 +4673,17 @@ error::Error GLES2DecoderImpl::HandleGetMaxValueInBufferCHROMIUM(
   return error::kNoError;
 }
 
+error::Error GLES2DecoderImpl::HandleDescheduleUntilFinishedCHROMIUM(
+    uint32_t immediate_data_size,
+    const void* cmd_data) {
+  const gles2::cmds::DescheduleUntilFinishedCHROMIUM& c =
+      *static_cast<const gles2::cmds::DescheduleUntilFinishedCHROMIUM*>(
+          cmd_data);
+  (void)c;
+  DoDescheduleUntilFinishedCHROMIUM();
+  return error::kNoError;

[piman, 2016/05/31 19:25:21]

You need to return kDeferCommandUntilLater here, otherwise the CommandExecutor
will happily continue executing the rest of the batch of commands and only later
realize that the command buffer is unscheduled and stop processing.

One thing though, kDeferCommandUntilLater is intended to break out before the
command executes, so it will not progress the "get" pointer, which means, when
rescheduled, it will try to re-execute the same command. 2 ways out: either keep
an extra state on GLES2DecoderImpl, or introduce another error state (e.g.
kDeferLaterCommands or kYieldCommandProcessing) to get out of the inner loop in
the CommandExecutor/CommandParser while still increasing the "get" pointer.

+}
+
 error::Error GLES2DecoderImpl::HandleTexImageIOSurface2DCHROMIUM(
     uint32_t immediate_data_size,
     const void* cmd_data) {