FYI, https://docs.google.com/document/d/1puS9pklOsPyk2CCRaCW3ZlEr8z30ruazAIJXHFHdB1s/edit# has detailed explanations about this conversion, including using base::AdaptCallbackForRepeating as a stopgap to wrap a OnceClosure.

This was blocking a different refactoring that I was doing (presubmit fails).

Patch is over here: https://chromium-review.googlesource.com/c/chromium/src/+/919245

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c

commit bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c
Author: Jonathan Backer <backer@chromium.org>
Date: Wed Feb 14 21:44:23 2018

Switch GpuControl to OnceClosure

Had to make GpuTask take both OnceClosure and RepeatingClosure so that
FlushOnGpuThread and be descheduled and then called again once it is
rescheduled. AFAICT, the other queued callbacks are called once.

Bug:  789349 
Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: Iaa89c4546436df2e0f5046d8330dbe40d349a93e
Reviewed-on: https://chromium-review.googlesource.com/919245
Reviewed-by: Bo <boliu@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Commit-Queue: Jonathan Backer <backer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536827}
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/android_webview/browser/deferred_gpu_command_service.cc
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/android_webview/browser/deferred_gpu_command_service.h
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/gpu/command_buffer/client/client_test_helper.h
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/gpu/command_buffer/client/gles2_implementation_unittest.cc
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/gpu/command_buffer/client/gpu_control.h
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/gpu/command_buffer/service/command_buffer_direct.cc
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/gpu/command_buffer/service/command_buffer_direct.h
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/gpu/command_buffer/tests/decoder_perftest.cc
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/gpu/command_buffer/tests/gl_manager.cc
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/gpu/command_buffer/tests/gl_manager.h
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/gpu/gles2_conform_support/egl/context.cc
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/gpu/gles2_conform_support/egl/context.h
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/gpu/ipc/client/command_buffer_proxy_impl.cc
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/gpu/ipc/client/command_buffer_proxy_impl.h
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/gpu/ipc/gpu_in_process_thread_service.cc
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/gpu/ipc/gpu_in_process_thread_service.h
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/gpu/ipc/in_process_command_buffer.cc
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/gpu/ipc/in_process_command_buffer.h
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/ppapi/proxy/ppapi_command_buffer_proxy.cc
[modify] https://crrev.com/bd345c1f0d8e51f91ddfd8b3f20d7011ac79d41c/ppapi/proxy/ppapi_command_buffer_proxy.h