GN: don't write separate files for non-binary targets

GN: don't write separate files for non-binary targets

Binary targets that compile code need to be in separate ninja files for the various flags variables to be properly scoped. But other targets like groups and actions don't. This change skips making separate files for such targets.

The target writers have changed to return the code they want written to the main ninja file, which is either all of the code (for the new integrated case) or a subninja line to reference a written file. This allowed some amount of cleanup in how the Ninja toolchain files were written.

The changes in the ninja toolchain files required more changes in the NinjaBuildWriter because the lists the NinjaBuildWriter were no longer being generated as a side effect of running. The build writer is now more isolated and can run without such precomputed context. There was a fair bit of refactoring required to make this work in ninja_build_writer.cc. Effectively the complexity in NinjaWriter moved to NinjaBuildWriter::RunAndWriteFiles.

A related cleanup is that I noticed the Builder object is RefCountedThreadsafe because it used to be used across threads. But a while ago I changes this to work on the main thread only. I removed the refcounting and changed most places to pass by reference instead of pointer.

GN runtime stats:
 - Desktop Linux: saves 2656 files, 110ms.
 - Android: saves 8825 files, 231ms.
 - Windows: saves 2203 files, 247ms.

Ninja no-op build stats (measures loading time):
 - Desktop Linux: same
 - Android: regressed 50ms (maybe because there's less parsing parallelism and Linux's filesystem is so fast?)
 - Windows: saves 156ms (because Windows' filesystem is so slow.

Committed: https://crrev.com/8293c354da7aee9e9a7130b3b6f67d9ea43a7230
Cr-Commit-Position: refs/heads/master@{#407908}

[brettw, 2016-07-19 16:31:12]

compiles

[brettw, 2016-07-19 19:50:45]

tests

[brettw, 2016-07-19 23:17:42]

Description was changed from

==========
Works except for default rules

BUG=
==========

to

==========
GN: don't write separate files for non-binary targets

Binary targets that compile code need to be in separate ninja files for the
various flags variables to be properly scoped. But other targets like groups and
actions don't. This change skips making separate files for such targets.

The target writers have changed to return the code they want written to the main
ninja file, which is either all of the code (for the new integrated case) or a
subninja line to reference a written file. This allowed some amount of cleanup
in how the Ninja toolchain files were written.

The changes in the ninja toolchain files required more changes in the
NinjaBuildWriter because the lists the NinjaBuildWriter were no longer being
generated as a side effect of running. The build writer is now more isolated and
can run without such precomputed context. There was a fair bit of refactoring
required to make this work in ninja_build_writer.cc

A related cleanup is that I noticed the Builder object is RefCountedThreadsafe
because it used to be used across threads. But a while ago I changes this to
work on the main thread only. I removed the refcounting and changed most places
to pass by reference instead of pointer.
==========

[brettw, 2016-07-19 23:20:39]

Description was changed from

==========
GN: don't write separate files for non-binary targets

Binary targets that compile code need to be in separate ninja files for the
various flags variables to be properly scoped. But other targets like groups and
actions don't. This change skips making separate files for such targets.

The target writers have changed to return the code they want written to the main
ninja file, which is either all of the code (for the new integrated case) or a
subninja line to reference a written file. This allowed some amount of cleanup
in how the Ninja toolchain files were written.

The changes in the ninja toolchain files required more changes in the
NinjaBuildWriter because the lists the NinjaBuildWriter were no longer being
generated as a side effect of running. The build writer is now more isolated and
can run without such precomputed context. There was a fair bit of refactoring
required to make this work in ninja_build_writer.cc

A related cleanup is that I noticed the Builder object is RefCountedThreadsafe
because it used to be used across threads. But a while ago I changes this to
work on the main thread only. I removed the refcounting and changed most places
to pass by reference instead of pointer.
==========

to

==========
GN: don't write separate files for non-binary targets

Binary targets that compile code need to be in separate ninja files for the
various flags variables to be properly scoped. But other targets like groups and
actions don't. This change skips making separate files for such targets.

The target writers have changed to return the code they want written to the main
ninja file, which is either all of the code (for the new integrated case) or a
subninja line to reference a written file. This allowed some amount of cleanup
in how the Ninja toolchain files were written.

The changes in the ninja toolchain files required more changes in the
NinjaBuildWriter because the lists the NinjaBuildWriter were no longer being
generated as a side effect of running. The build writer is now more isolated and
can run without such precomputed context. There was a fair bit of refactoring
required to make this work in ninja_build_writer.cc

A related cleanup is that I noticed the Builder object is RefCountedThreadsafe
because it used to be used across threads. But a while ago I changes this to
work on the main thread only. I removed the refcounting and changed most places
to pass by reference instead of pointer.

GN runtime stats:
 - Desktop Linux: saves 2656 files, 110ms.
 - Android: saves 8825 files, 231ms.
 - Windows: saves 2203 files, 247ms.

Ninja no-op stats are the same on desktop Linux, regressed by 50ms for Android
(maybe because there's less parsing parallelism and Linux's filesystem is so
fast?), and improved by 156ms on Windows (because Windows' filesystem is so
slow).
==========

[brettw, 2016-07-19 23:22:17]

Description was changed from

==========
GN: don't write separate files for non-binary targets

Binary targets that compile code need to be in separate ninja files for the
various flags variables to be properly scoped. But other targets like groups and
actions don't. This change skips making separate files for such targets.

The target writers have changed to return the code they want written to the main
ninja file, which is either all of the code (for the new integrated case) or a
subninja line to reference a written file. This allowed some amount of cleanup
in how the Ninja toolchain files were written.

The changes in the ninja toolchain files required more changes in the
NinjaBuildWriter because the lists the NinjaBuildWriter were no longer being
generated as a side effect of running. The build writer is now more isolated and
can run without such precomputed context. There was a fair bit of refactoring
required to make this work in ninja_build_writer.cc

A related cleanup is that I noticed the Builder object is RefCountedThreadsafe
because it used to be used across threads. But a while ago I changes this to
work on the main thread only. I removed the refcounting and changed most places
to pass by reference instead of pointer.

GN runtime stats:
 - Desktop Linux: saves 2656 files, 110ms.
 - Android: saves 8825 files, 231ms.
 - Windows: saves 2203 files, 247ms.

Ninja no-op stats are the same on desktop Linux, regressed by 50ms for Android
(maybe because there's less parsing parallelism and Linux's filesystem is so
fast?), and improved by 156ms on Windows (because Windows' filesystem is so
slow).
==========

to

==========
GN: don't write separate files for non-binary targets

Binary targets that compile code need to be in separate ninja files for the
various flags variables to be properly scoped. But other targets like groups and
actions don't. This change skips making separate files for such targets.

The target writers have changed to return the code they want written to the main
ninja file, which is either all of the code (for the new integrated case) or a
subninja line to reference a written file. This allowed some amount of cleanup
in how the Ninja toolchain files were written.

The changes in the ninja toolchain files required more changes in the
NinjaBuildWriter because the lists the NinjaBuildWriter were no longer being
generated as a side effect of running. The build writer is now more isolated and
can run without such precomputed context. There was a fair bit of refactoring
required to make this work in ninja_build_writer.cc

A related cleanup is that I noticed the Builder object is RefCountedThreadsafe
because it used to be used across threads. But a while ago I changes this to
work on the main thread only. I removed the refcounting and changed most places
to pass by reference instead of pointer.

GN runtime stats:
 - Desktop Linux: saves 2656 files, 110ms.
 - Android: saves 8825 files, 231ms.
 - Windows: saves 2203 files, 247ms.

Ninja no-op stats:
 - Desktop Linux: same
 - Android: regressed 50ms (maybe because there's less parsing parallelism and
Linux's filesystem is so fast?)
 - Windows:saves 156ms (because Windows' filesystem is so slow.
==========

[brettw, 2016-07-19 23:22:38]

Description was changed from

==========
GN: don't write separate files for non-binary targets

Binary targets that compile code need to be in separate ninja files for the
various flags variables to be properly scoped. But other targets like groups and
actions don't. This change skips making separate files for such targets.

The target writers have changed to return the code they want written to the main
ninja file, which is either all of the code (for the new integrated case) or a
subninja line to reference a written file. This allowed some amount of cleanup
in how the Ninja toolchain files were written.

The changes in the ninja toolchain files required more changes in the
NinjaBuildWriter because the lists the NinjaBuildWriter were no longer being
generated as a side effect of running. The build writer is now more isolated and
can run without such precomputed context. There was a fair bit of refactoring
required to make this work in ninja_build_writer.cc

A related cleanup is that I noticed the Builder object is RefCountedThreadsafe
because it used to be used across threads. But a while ago I changes this to
work on the main thread only. I removed the refcounting and changed most places
to pass by reference instead of pointer.

GN runtime stats:
 - Desktop Linux: saves 2656 files, 110ms.
 - Android: saves 8825 files, 231ms.
 - Windows: saves 2203 files, 247ms.

Ninja no-op stats:
 - Desktop Linux: same
 - Android: regressed 50ms (maybe because there's less parsing parallelism and
Linux's filesystem is so fast?)
 - Windows:saves 156ms (because Windows' filesystem is so slow.
==========

to

==========
GN: don't write separate files for non-binary targets

Binary targets that compile code need to be in separate ninja files for the
various flags variables to be properly scoped. But other targets like groups and
actions don't. This change skips making separate files for such targets.

The target writers have changed to return the code they want written to the main
ninja file, which is either all of the code (for the new integrated case) or a
subninja line to reference a written file. This allowed some amount of cleanup
in how the Ninja toolchain files were written.

The changes in the ninja toolchain files required more changes in the
NinjaBuildWriter because the lists the NinjaBuildWriter were no longer being
generated as a side effect of running. The build writer is now more isolated and
can run without such precomputed context. There was a fair bit of refactoring
required to make this work in ninja_build_writer.cc

A related cleanup is that I noticed the Builder object is RefCountedThreadsafe
because it used to be used across threads. But a while ago I changes this to
work on the main thread only. I removed the refcounting and changed most places
to pass by reference instead of pointer.

GN runtime stats:
 - Desktop Linux: saves 2656 files, 110ms.
 - Android: saves 8825 files, 231ms.
 - Windows: saves 2203 files, 247ms.

Ninja no-op build stats (measures loading time):
 - Desktop Linux: same
 - Android: regressed 50ms (maybe because there's less parsing parallelism and
Linux's filesystem is so fast?)
 - Windows:saves 156ms (because Windows' filesystem is so slow.
==========

[brettw, 2016-07-19 23:22:58]

Description was changed from

==========
GN: don't write separate files for non-binary targets

Binary targets that compile code need to be in separate ninja files for the
various flags variables to be properly scoped. But other targets like groups and
actions don't. This change skips making separate files for such targets.

The target writers have changed to return the code they want written to the main
ninja file, which is either all of the code (for the new integrated case) or a
subninja line to reference a written file. This allowed some amount of cleanup
in how the Ninja toolchain files were written.

The changes in the ninja toolchain files required more changes in the
NinjaBuildWriter because the lists the NinjaBuildWriter were no longer being
generated as a side effect of running. The build writer is now more isolated and
can run without such precomputed context. There was a fair bit of refactoring
required to make this work in ninja_build_writer.cc

A related cleanup is that I noticed the Builder object is RefCountedThreadsafe
because it used to be used across threads. But a while ago I changes this to
work on the main thread only. I removed the refcounting and changed most places
to pass by reference instead of pointer.

GN runtime stats:
 - Desktop Linux: saves 2656 files, 110ms.
 - Android: saves 8825 files, 231ms.
 - Windows: saves 2203 files, 247ms.

Ninja no-op build stats (measures loading time):
 - Desktop Linux: same
 - Android: regressed 50ms (maybe because there's less parsing parallelism and
Linux's filesystem is so fast?)
 - Windows:saves 156ms (because Windows' filesystem is so slow.
==========

to

==========
GN: don't write separate files for non-binary targets

Binary targets that compile code need to be in separate ninja files for the
various flags variables to be properly scoped. But other targets like groups and
actions don't. This change skips making separate files for such targets.

The target writers have changed to return the code they want written to the main
ninja file, which is either all of the code (for the new integrated case) or a
subninja line to reference a written file. This allowed some amount of cleanup
in how the Ninja toolchain files were written.

The changes in the ninja toolchain files required more changes in the
NinjaBuildWriter because the lists the NinjaBuildWriter were no longer being
generated as a side effect of running. The build writer is now more isolated and
can run without such precomputed context. There was a fair bit of refactoring
required to make this work in ninja_build_writer.cc

A related cleanup is that I noticed the Builder object is RefCountedThreadsafe
because it used to be used across threads. But a while ago I changes this to
work on the main thread only. I removed the refcounting and changed most places
to pass by reference instead of pointer.

GN runtime stats:
 - Desktop Linux: saves 2656 files, 110ms.
 - Android: saves 8825 files, 231ms.
 - Windows: saves 2203 files, 247ms.

Ninja no-op build stats (measures loading time):
 - Desktop Linux: same
 - Android: regressed 50ms (maybe because there's less parsing parallelism and
Linux's filesystem is so fast?)
 - Windows: saves 156ms (because Windows' filesystem is so slow.
==========

[brettw, 2016-07-19 23:27:59]

Description was changed from

==========
GN: don't write separate files for non-binary targets

Binary targets that compile code need to be in separate ninja files for the
various flags variables to be properly scoped. But other targets like groups and
actions don't. This change skips making separate files for such targets.

The target writers have changed to return the code they want written to the main
ninja file, which is either all of the code (for the new integrated case) or a
subninja line to reference a written file. This allowed some amount of cleanup
in how the Ninja toolchain files were written.

The changes in the ninja toolchain files required more changes in the
NinjaBuildWriter because the lists the NinjaBuildWriter were no longer being
generated as a side effect of running. The build writer is now more isolated and
can run without such precomputed context. There was a fair bit of refactoring
required to make this work in ninja_build_writer.cc

A related cleanup is that I noticed the Builder object is RefCountedThreadsafe
because it used to be used across threads. But a while ago I changes this to
work on the main thread only. I removed the refcounting and changed most places
to pass by reference instead of pointer.

GN runtime stats:
 - Desktop Linux: saves 2656 files, 110ms.
 - Android: saves 8825 files, 231ms.
 - Windows: saves 2203 files, 247ms.

Ninja no-op build stats (measures loading time):
 - Desktop Linux: same
 - Android: regressed 50ms (maybe because there's less parsing parallelism and
Linux's filesystem is so fast?)
 - Windows: saves 156ms (because Windows' filesystem is so slow.
==========

to

==========
GN: don't write separate files for non-binary targets

Binary targets that compile code need to be in separate ninja files for the
various flags variables to be properly scoped. But other targets like groups and
actions don't. This change skips making separate files for such targets.

The target writers have changed to return the code they want written to the main
ninja file, which is either all of the code (for the new integrated case) or a
subninja line to reference a written file. This allowed some amount of cleanup
in how the Ninja toolchain files were written.

The changes in the ninja toolchain files required more changes in the
NinjaBuildWriter because the lists the NinjaBuildWriter were no longer being
generated as a side effect of running. The build writer is now more isolated and
can run without such precomputed context. There was a fair bit of refactoring
required to make this work in ninja_build_writer.cc. Effectively the complexity
in NinjaWriter moved to NinjaBuildWriter::RunAndWriteFiles.

A related cleanup is that I noticed the Builder object is RefCountedThreadsafe
because it used to be used across threads. But a while ago I changes this to
work on the main thread only. I removed the refcounting and changed most places
to pass by reference instead of pointer.

GN runtime stats:
 - Desktop Linux: saves 2656 files, 110ms.
 - Android: saves 8825 files, 231ms.
 - Windows: saves 2203 files, 247ms.

Ninja no-op build stats (measures loading time):
 - Desktop Linux: same
 - Android: regressed 50ms (maybe because there's less parsing parallelism and
Linux's filesystem is so fast?)
 - Windows: saves 156ms (because Windows' filesystem is so slow.
==========

[brettw, 2016-07-19 23:28:05]

The CQ bit was checked by brettw@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-07-19 23:29:07]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-07-19 23:51:22]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-07-19 23:51:23]

Dry run: Try jobs failed on following builders:
  win_chromium_x64_rel_ng on master.tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_x64_...)

[brettw, 2016-07-20 17:47:53]

win_test_fixes

[brettw, 2016-07-20 17:47:54]

The CQ bit was checked by brettw@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-07-20 17:48:21]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[brettw, 2016-07-20 18:00:02]

brettw@chromium.org changed reviewers:
+ brucedawson@chromium.org

[brettw, 2016-07-20 18:00:03]

Low priority (doesn't affect GN transition). Over the no-meetings week I
finished up this patch which I've been working on in various forms for a while.

[commit-bot: I haz the power, 2016-07-20 18:30:50]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-07-20 18:30:51]

Dry run: This issue passed the CQ dry run.

[brucedawson, 2016-07-25 17:38:00]

It might have been better to separate the reference-count change from the other
change to make it easier to see the interesting changes versus the mechanical.
But, no matter.

I'm afraid I don't understand the code well but it seems good. lgtm with one
comment nit.

https://codereview.chromium.org/2152413002/diff/100001/tools/gn/ninja_target_...
File tools/gn/ninja_target_writer.h (right):

https://codereview.chromium.org/2152413002/diff/100001/tools/gn/ninja_target_...
tools/gn/ninja_target_writer.h:29: // Some targets have their rules get written
to separate files, and some
"rules get written" -> "rules written"

[brettw, 2016-07-26 17:52:23]

typo

[brettw, 2016-07-26 17:52:24]

The CQ bit was checked by brettw@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-07-26 17:52:51]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-07-26 18:32:55]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-07-26 18:32:56]

Dry run: This issue passed the CQ dry run.

[brettw, 2016-07-26 19:21:16]

The CQ bit was checked by brettw@chromium.org

[brettw, 2016-07-26 19:21:16]

The patchset sent to the CQ was uploaded after l-g-t-m from
brucedawson@chromium.org
Link to the patchset: https://codereview.chromium.org/2152413002/#ps140001
(title: "typo")

[brettw, 2016-07-26 19:21:26]

The CQ bit was unchecked by brettw@chromium.org

[brettw, 2016-07-26 20:31:35]

The CQ bit was checked by brettw@chromium.org

[commit-bot: I haz the power, 2016-07-26 20:32:47]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-07-26 20:38:51]

Description was changed from

==========
GN: don't write separate files for non-binary targets

Binary targets that compile code need to be in separate ninja files for the
various flags variables to be properly scoped. But other targets like groups and
actions don't. This change skips making separate files for such targets.

The target writers have changed to return the code they want written to the main
ninja file, which is either all of the code (for the new integrated case) or a
subninja line to reference a written file. This allowed some amount of cleanup
in how the Ninja toolchain files were written.

The changes in the ninja toolchain files required more changes in the
NinjaBuildWriter because the lists the NinjaBuildWriter were no longer being
generated as a side effect of running. The build writer is now more isolated and
can run without such precomputed context. There was a fair bit of refactoring
required to make this work in ninja_build_writer.cc. Effectively the complexity
in NinjaWriter moved to NinjaBuildWriter::RunAndWriteFiles.

A related cleanup is that I noticed the Builder object is RefCountedThreadsafe
because it used to be used across threads. But a while ago I changes this to
work on the main thread only. I removed the refcounting and changed most places
to pass by reference instead of pointer.

GN runtime stats:
 - Desktop Linux: saves 2656 files, 110ms.
 - Android: saves 8825 files, 231ms.
 - Windows: saves 2203 files, 247ms.

Ninja no-op build stats (measures loading time):
 - Desktop Linux: same
 - Android: regressed 50ms (maybe because there's less parsing parallelism and
Linux's filesystem is so fast?)
 - Windows: saves 156ms (because Windows' filesystem is so slow.
==========

to

==========
GN: don't write separate files for non-binary targets

Binary targets that compile code need to be in separate ninja files for the
various flags variables to be properly scoped. But other targets like groups and
actions don't. This change skips making separate files for such targets.

The target writers have changed to return the code they want written to the main
ninja file, which is either all of the code (for the new integrated case) or a
subninja line to reference a written file. This allowed some amount of cleanup
in how the Ninja toolchain files were written.

The changes in the ninja toolchain files required more changes in the
NinjaBuildWriter because the lists the NinjaBuildWriter were no longer being
generated as a side effect of running. The build writer is now more isolated and
can run without such precomputed context. There was a fair bit of refactoring
required to make this work in ninja_build_writer.cc. Effectively the complexity
in NinjaWriter moved to NinjaBuildWriter::RunAndWriteFiles.

A related cleanup is that I noticed the Builder object is RefCountedThreadsafe
because it used to be used across threads. But a while ago I changes this to
work on the main thread only. I removed the refcounting and changed most places
to pass by reference instead of pointer.

GN runtime stats:
 - Desktop Linux: saves 2656 files, 110ms.
 - Android: saves 8825 files, 231ms.
 - Windows: saves 2203 files, 247ms.

Ninja no-op build stats (measures loading time):
 - Desktop Linux: same
 - Android: regressed 50ms (maybe because there's less parsing parallelism and
Linux's filesystem is so fast?)
 - Windows: saves 156ms (because Windows' filesystem is so slow.
==========

[commit-bot: I haz the power, 2016-07-26 20:38:52]

Committed patchset #8 (id:140001)

[commit-bot: I haz the power, 2016-07-26 20:40:45]

Description was changed from

==========
GN: don't write separate files for non-binary targets

Binary targets that compile code need to be in separate ninja files for the
various flags variables to be properly scoped. But other targets like groups and
actions don't. This change skips making separate files for such targets.

The target writers have changed to return the code they want written to the main
ninja file, which is either all of the code (for the new integrated case) or a
subninja line to reference a written file. This allowed some amount of cleanup
in how the Ninja toolchain files were written.

The changes in the ninja toolchain files required more changes in the
NinjaBuildWriter because the lists the NinjaBuildWriter were no longer being
generated as a side effect of running. The build writer is now more isolated and
can run without such precomputed context. There was a fair bit of refactoring
required to make this work in ninja_build_writer.cc. Effectively the complexity
in NinjaWriter moved to NinjaBuildWriter::RunAndWriteFiles.

A related cleanup is that I noticed the Builder object is RefCountedThreadsafe
because it used to be used across threads. But a while ago I changes this to
work on the main thread only. I removed the refcounting and changed most places
to pass by reference instead of pointer.

GN runtime stats:
 - Desktop Linux: saves 2656 files, 110ms.
 - Android: saves 8825 files, 231ms.
 - Windows: saves 2203 files, 247ms.

Ninja no-op build stats (measures loading time):
 - Desktop Linux: same
 - Android: regressed 50ms (maybe because there's less parsing parallelism and
Linux's filesystem is so fast?)
 - Windows: saves 156ms (because Windows' filesystem is so slow.
==========

to

==========
GN: don't write separate files for non-binary targets

Binary targets that compile code need to be in separate ninja files for the
various flags variables to be properly scoped. But other targets like groups and
actions don't. This change skips making separate files for such targets.

The target writers have changed to return the code they want written to the main
ninja file, which is either all of the code (for the new integrated case) or a
subninja line to reference a written file. This allowed some amount of cleanup
in how the Ninja toolchain files were written.

The changes in the ninja toolchain files required more changes in the
NinjaBuildWriter because the lists the NinjaBuildWriter were no longer being
generated as a side effect of running. The build writer is now more isolated and
can run without such precomputed context. There was a fair bit of refactoring
required to make this work in ninja_build_writer.cc. Effectively the complexity
in NinjaWriter moved to NinjaBuildWriter::RunAndWriteFiles.

A related cleanup is that I noticed the Builder object is RefCountedThreadsafe
because it used to be used across threads. But a while ago I changes this to
work on the main thread only. I removed the refcounting and changed most places
to pass by reference instead of pointer.

GN runtime stats:
 - Desktop Linux: saves 2656 files, 110ms.
 - Android: saves 8825 files, 231ms.
 - Windows: saves 2203 files, 247ms.

Ninja no-op build stats (measures loading time):
 - Desktop Linux: same
 - Android: regressed 50ms (maybe because there's less parsing parallelism and
Linux's filesystem is so fast?)
 - Windows: saves 156ms (because Windows' filesystem is so slow.

Committed: https://crrev.com/8293c354da7aee9e9a7130b3b6f67d9ea43a7230
Cr-Commit-Position: refs/heads/master@{#407908}
==========

[commit-bot: I haz the power, 2016-07-26 20:40:46]

Patchset 8 (id:??) landed as
https://crrev.com/8293c354da7aee9e9a7130b3b6f67d9ea43a7230
Cr-Commit-Position: refs/heads/master@{#407908}