Reland of gpu: GPU service scheduler. (patchset #1 id:1 of...

Reland of gpu: GPU service scheduler. (patchset #1 id:1 of https://codereview.chromium.org/2881813002/ )

Reason for revert:
remove incorrect dcheck

Original issue's description:
> Revert of gpu: GPU service scheduler. (patchset #18 id:340001 of https://codereview.chromium.org/2814843002/ )
>
> Reason for revert:
> Suspected of breaking the Win7 Tests (dbg)(1) builder:
>
> https://build.chromium.org/p/chromium.win/builders/Win7%20Tests%20%28dbg%29%281%29/builds/59869
>
> Sample stack trace:
>
> [6424:6796:0512/085713.197:FATAL:gpu_channel.cc(122)] Check failed: channel_messages_.empty().
> Backtrace:
> 	base::debug::StackTrace::StackTrace [0x100AD557+55]
> 	base::debug::StackTrace::StackTrace [0x100AD1F1+17]
> 	logging::LogMessage::~LogMessage [0x1010103E+94]
> 	gpu::GpuChannelMessageQueue::~GpuChannelMessageQueue [0x0AA6A1DE+126]
> 	gpu::GpuChannelMessageQueue::`scalar deleting destructor' [0x0AA6D13F+15]
> 	base::RefCountedThreadSafe<gpu::GpuChannelMessageQueue,base::DefaultRefCountedThreadSafeTraits<gpu::GpuChannelMessageQueue> >::DeleteInternal [0x0AA6E4A2+34]
> 	base::DefaultRefCountedThreadSafeTraits<gpu::GpuChannelMessageQueue>::Destruct [0x0AA6E7BC+12]
> 	base::RefCountedThreadSafe<gpu::GpuChannelMessageQueue,base::DefaultRefCountedThreadSafeTraits<gpu::GpuChannelMessageQueue> >::Release [0x0AA731D0+32]
> 	scoped_refptr<gpu::GpuChannelMessageQueue>::Release [0x0AA7323B+11]
> 	scoped_refptr<gpu::GpuChannelMessageQueue>::~scoped_refptr<gpu::GpuChannelMessageQueue> [0x0AA69A5A+26]
> 	gpu::GpuChannelMessageFilter::~GpuChannelMessageFilter [0x0AA6A0F7+151]
> 	gpu::GpuChannelMessageFilter::`vector deleting destructor' [0x0AA6CC4D+77]
> 	base::RefCountedThreadSafe<IPC::MessageFilter,base::DefaultRefCountedThreadSafeTraits<IPC::MessageFilter> >::DeleteInternal [0x0B154D27+39]
> 	base::DefaultRefCountedThreadSafeTraits<IPC::MessageFilter>::Destruct [0x0B154F3C+12]
> 	base::RefCountedThreadSafe<IPC::MessageFilter,base::DefaultRefCountedThreadSafeTraits<IPC::MessageFilter> >::Release [0x0B1565DA+58]
> 	scoped_refptr<IPC::MessageFilter>::Release [0x0B15662E+14]
> 	scoped_refptr<IPC::MessageFilter>::~scoped_refptr<IPC::MessageFilter> [0x0B152A7A+26]
> 	scoped_refptr<IPC::MessageFilter>::`scalar deleting destructor' [0x0B15411F+15]
> 	std::allocator<scoped_refptr<IPC::MessageFilter> >::destroy<scoped_refptr<IPC::MessageFilter> > [0x0B151261+17]
> 	std::allocator_traits<std::allocator<scoped_refptr<IPC::MessageFilter> > >::destroy<scoped_refptr<IPC::MessageFilter> > [0x0B15127F+15]
> 	std::_Wrap_alloc<std::allocator<scoped_refptr<IPC::MessageFilter> > >::destroy<scoped_refptr<IPC::MessageFilter> > [0x0B151234+20]
> 	std::_Destroy_range1<std::allocator<scoped_refptr<IPC::MessageFilter> >,scoped_refptr<IPC::MessageFilter> *> [0x0B15074B+43]
> 	std::_Destroy_range<std::allocator<scoped_refptr<IPC::MessageFilter> >,scoped_refptr<IPC::MessageFilter> *> [0x0B1507AA+26]
> 	std::vector<scoped_refptr<IPC::MessageFilter>,std::allocator<scoped_refptr<IPC::MessageFilter> > >::_Destroy [0x0B15740D+29]
> 	std::vector<scoped_refptr<IPC::MessageFilter>,std::allocator<scoped_refptr<IPC::MessageFilter> > >::clear [0x0B15878E+46]
> 	IPC::ChannelProxy::Context::OnChannelClosed [0x0B1558EB+395]
> 	IPC::SyncChannel::SyncContext::OnChannelClosed [0x0B190416+38]
> 	??$Invoke@ABV?$scoped_refptr@VContext@ChannelProxy@IPC@@@@$$V@?$FunctorTraits@P8Context@ChannelProxy@IPC@@AEXXZX@internal@base@@SAXP8Context@ChannelProxy@IPC@@AEXXZABV?$scoped_refptr@VContext@ChannelProxy@IPC@@@@@Z [0x0B14F978+24]
> 	base::internal::InvokeHelper<0,void>::MakeItSo<void (__thiscall IPC::ChannelProxy::Context::*const &)(void),scoped_refptr<IPC::ChannelProxy::Context> const &> [0x0B1500B8+40]
> 	base::internal::Invoker<base::internal::BindState<void (__thiscall IPC::ChannelProxy::Context::*)(void),scoped_refptr<IPC::ChannelProxy::Context> >,void __cdecl(void)>::RunImpl<void (__thiscall IPC::ChannelProxy::Context::*const &)(void),std::tuple<scoped [0x0B1504A4+52]
> 	base::internal::Invoker<base::internal::BindState<void (__thiscall IPC::ChannelProxy::Context::*)(void),scoped_refptr<IPC::ChannelProxy::Context> >,void __cdecl(void)>::Run [0x0B156904+36]
> 	base::Callback<void __cdecl(void),0,0>::Run [0x10049A45+53]
> 	base::debug::TaskAnnotator::RunTask [0x100B444C+476]
> 	base::MessageLoop::RunTask [0x1012F94C+620]
> 	base::MessageLoop::DeferOrRunPendingTask [0x1012DE4B+43]
> 	base::MessageLoop::DoWork [0x1012E44F+239]
> 	base::MessagePumpForIO::DoRunLoop [0x10136211+33]
> 	base::MessagePumpWin::Run [0x101372FB+123]
> 	base::MessageLoop::RunHandler [0x1012F5C5+293]
> 	base::RunLoop::Run [0x101EDB26+166]
> 	base::Thread::Run [0x10289D01+273]
> 	base::Thread::ThreadMain [0x1028AE4F+863]
> 	base::PlatformThread::Sleep [0x102659EC+380]
> 	BaseThreadInitThunk [0x76A9338A+18]
> 	RtlInitializeExceptionChain [0x77A39902+99]
> 	RtlInitializeExceptionChain [0x77A398D5+54]
>
> Original issue's description:
> > gpu: GPU service scheduler.
> >
> > The GPU service scheduler runs tasks (closures) containing command
> > buffer work. Tasks are enqueued in sequences which represent indepdent
> > streams of execution. A task in one sequence may wait on a sync token
> > fence that's released on another sequence. Tasks can specify their sync
> > token fences beforehand so that the scheduler won't run a sequence only
> > to disable it due to a sync token wait. Tasks can check if they should
> > yield so that a higher priority task may run. If a task decides to
> > yield, it can continue execution by supplying a new closure which will
> > run before any other scheduled tasks in that sequence.
> >
> > The scheduler maintains a priority queue of sequences ordered by
> > sequence priority and then order number. Priority inversion because of
> > sync token dependencies is handled by a simple priority ceiling scheme.
> > Sequences which are expected to release sync tokens dependencies are
> > assigned a priority (HIGH) that's higher than any client specified
> > priorities. However, browser view context sequences can have an even
> > higher priority (REAL_TIME).
> >
> > GPU channel IPC messages are run as tasks in the scheduler. Each client
> > side stream is mapped to a sequence. The client is expected to use a
> > small number of streams to partition its command buffers so there is no
> > tracking of stream lifetimes in the service. The message filter posts
> > messages as tasks. AsyncFlush is the only message for which sync token
> > dependencies are given to the scheduler.
> >
> > The initial implementation uses the GPU main thread to run scheduled
> > tasks. Future implementations, for example, could use a worker pool
> > with task traits to specify which thread a task should run on.
> >
> > R=piman@chromium.org
> > BUG=514813
> > CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel;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
> >
> > Review-Url: https://codereview.chromium.org/2814843002
> > Cr-Commit-Position: refs/heads/master@{#471187}
> > Committed: https://chromium.googlesource.com/chromium/src/+/e7e36ccdaa3fcf63b330bc956eeeb73abf7c39ea
>
> TBR=piman@chromium.org,vmiura@chromium.org,dcheng@chromium.org,sadrul@chromium.org,sunnyps@chromium.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=514813
>
> Review-Url: https://codereview.chromium.org/2881813002
> Cr-Commit-Position: refs/heads/master@{#471335}
> Committed: https://chromium.googlesource.com/chromium/src/+/9d3cbf5bb0cca7fdcbfa22c63a18008e242f3bc9

TBR=piman@chromium.org,vmiura@chromium.org,dcheng@chromium.org,sadrul@chromium.org,jdonnelly@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=514813
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

Review-Url: https://codereview.chromium.org/2876913003
Cr-Commit-Position: refs/heads/master@{#471361}