Roll GN from r1496 (0790d304) to r1546 (b85982b3)

Now that we can use CIPD to install GN binaries, we can finally
roll GN and catch up w/ multiple months of changes :)

    https://gn.googlesource.com/gn.git/+log/0790d304..b85982b

    b85982b3 visual_studio_writer: Make OutDir equal to $(SolutionDir).
    9434c3d2 Make gen.py compatible with python3
    b199e54b [docs] : Split 'gn help' heading and usage summary when exceed 80 cols
    5bc90b63 stdout: use dim colors
    24411bec Make gn check faster
    3941394b [docs] regenerate docs/reference.md
    93ac4e04 Some documentation of gn check --check-generated
    fd1532f2 [docs] Fix Markdown format missing `
    74657a61 Add gn check --check-generated to check dependencies of generated files
    6b943827 Fixed typo (missing parenthesis) in get_path_info documentation
    d062e74f Improve config documentation.
    e15f243a gen.py: Pass -pthread, not -lpthread, in ldflags.
    013513c9 gn recipe: Do not pass libraries in LDFLAGS in the Linux recipe
    1152229e gen.py: Pass -pthread via ldflags, not libs
    01237e9c Remove references to ARM-optimized math implementation
    0ac93dd2 For proper order put -lpthreads as a 'library' not a 'linker flag'
    1ab6fa2c Attempt to unbreak build with MSVC 15.8.4
    082fbe39 Pass -lpthread when linking instead of -pthread
    d69a9c37 [help] Fixing help issues.
    04685d69 Add --dump-json-tree option for format subcommand.
    57586fdb Suppress warning on VS2017.
    4dcd2776 Port to FreeBSD.
    5519dc2f Reintroduce the ICF flag, turn it on for bots
    53107bfc [infra] Update XCode version
    377ad041 Enable LTO for release builds
    282a428c Disable ICF on Darwin, make it default for Release
    71b537ce [format] Extend `gn format` to take a list of files.
    b5a2ac6e Improve help output.
    d837047a format: Ensure that formatting always reaches a fixedpoint in one run
    8ed01d3b Docs: regenerate docs
    d84a862e More efficient Value implementation.
    bcfb6471 cleanup label_ptr.h
    88bd8a8d build/gen.py: Add --no-strip option.
    894143c3 format: Fix incorrect dewrap of `if`
    45314e29 [metadata] Return metadata in postorder.
    e49432fa [metadata] Actually collect the metadata
    c1780c21 [metadata] Allow specification of rebase dir
    5a9e0a2c [metadata] Adding metadata vars to write_data target
    d021d391 [metadata] Add generated_file target type
    27b66b57 Allow whitespace in include directives.
    c6841d31 Fix a crash on invalid on `not_needed(scope)` without a 2nd argument.
    54be6f11 Allow NOSORT to be the last line in a comment in addition to the first.
    a07831bb [metadata] Adding `meta` command
    0587778f [metadata] Walk function
    96c77296 [metadata] Add metadata walk to target
    a27e8dc0 [metadata] Adding basic metadata walking
    2000587b [metadata] Adding metadata output to gn desc
    0e1b8843 [metadata] Adding metadata variable to target
    ecc95221 Add links to the "Using GN build" presentation.
    13ac6ca4 Test that not_needed works with forward_variables_from

Change-Id: I8db493df2a27c9b8ffe066a11179ffedb2b0f47a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1522549
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#645379}

DEPS

@@ -287,7 +287,7 @@ vars = {
   # revisions.
 
   # GN CIPD package version.
-  'gn_version': 'git_revision:0790d3043387c762a6bacb1ae0a9ebe883188ab2',
+  'gn_version': 'git_revision:b85982b3cb9b3971173f77c7575b53b3ac00e774',
 
   # Also, if you change these, make sure you update the svn_revisions in
   # //buildtools/deps_revisions.gni.

buildtools/DEPS

@@ -14,7 +14,7 @@ vars = {
   #
 
   # GN CIPD package version.
-  'gn_version': 'git_revision:0790d3043387c762a6bacb1ae0a9ebe883188ab2',
+  'gn_version': 'git_revision:b85982b3cb9b3971173f77c7575b53b3ac00e774',
 
   # When changing these, also update the svn revisions in deps_revisions.gni
   'clang_format_revision': '96636aa0e9f047f17447f2d45a094d0b59ed7917',