gpu: Add a new extension CHROMIUM_deschedule.

gpu/command_buffer/service/gles2_cmd_decoder_autogen.h

 // Copyright 2014 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.
 
 // This file is auto-generated from
 // gpu/command_buffer/build_gles2_cmd_buffer.py
 // It's formatted by clang-format using chromium coding style:
 //    clang-format -i -style=chromium filename
 // DO NOT EDIT!
 
@@ skipping 4655 matching lines @@
   }
   if (!validators_->get_max_index_type.IsValid(type)) {
     LOCAL_SET_GL_ERROR_INVALID_ENUM("glGetMaxValueInBufferCHROMIUM", type,
                                     "type");
     return error::kNoError;
   }
   *result_dst = DoGetMaxValueInBufferCHROMIUM(buffer_id, count, type, offset);
   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) {
   const gles2::cmds::TexImageIOSurface2DCHROMIUM& c =
       *static_cast<const gles2::cmds::TexImageIOSurface2DCHROMIUM*>(cmd_data);
   (void)c;
   GLenum target = static_cast<GLenum>(c.target);
   GLsizei width = static_cast<GLsizei>(c.width);
   GLsizei height = static_cast<GLsizei>(c.height);
   GLuint ioSurfaceId = static_cast<GLuint>(c.ioSurfaceId);
@@ skipping 624 matching lines @@
         state_.enable_flags.cached_sample_alpha_to_one_ext = enabled;
         return true;
       }
       return false;
     default:
       NOTREACHED();
       return false;
   }
 }
 #endif  // GPU_COMMAND_BUFFER_SERVICE_GLES2_CMD_DECODER_AUTOGEN_H_