Roll GN from 152c5144..ad9e442d

    ad9e442d Rename typefdefs for C++17
    dba3084e Define StringPiece in terms of std::string_view
    102cdd4b Define string16 in terms of std::u16string.
    b3fefa62 Compile with C++17.
    2a6c4e12 [windows] Update Windows SDK to 2019-09-06
    2a5b5ca0 Fix typo in linker section of docs.
    2f527608 [cleanup] Remove stale documentation from get_target_outputs.
    fc2f07a8 Add reference to the mailing list to the README.
    ad9054d1 gen.py: Allow linking libstdc++ dynamically
    6f3dad1a Don't use a nested scope for BUILDCONFIG.
    d9bbb45c Teach gn to handle systems with > 64 processors
    bac5bd0b Do not use the root scope for BUILDCONFIG.gn.
    8dc294d0 Write Rust deps even if there are only non-Rust ones
    21242330 Make "gn format" honor the global -q switch
    570aaed1 Process transitive dependecies for externs
    4dc0ce4d Update quick start guide to reference tutorial files
    f0a6900f Include Rust proc-macros as externs
    1556546b [filesystem_utils] Fix a bug in MakeAbsolutePathRelativeIfPossible
    dca877f3 Support output_dir for Rust
    0a73c484 Fix crash when sources is set to a non-list value
    0bc16a82 [args] Ensure gn tracelog is processed when non-fatal error happens.

Change-Id: I4ef0406f0deb636eb3213a480f73dff06059d971
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1793533Reviewed-by: Brett Wilson <brettw@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#695044}

DEPS

@@ -316,7 +316,7 @@ vars = {
   # revisions.
 
   # GN CIPD package version.
-  'gn_version': 'git_revision:152c5144ceed9592c20f0c8fd55769646077569b',
+  'gn_version': 'git_revision:ad9e442d92dcd9ee73a557428cfc336b55cbd533',
 
   # Also, if you change these, update buildtools/DEPS too. Also update the
   # libc++ svn_revision in //buildtools/deps_revisions.gni.

buildtools/DEPS

@@ -14,7 +14,7 @@ vars = {
   #
 
   # GN CIPD package version.
-  'gn_version': 'git_revision:152c5144ceed9592c20f0c8fd55769646077569b',
+  'gn_version': 'git_revision:ad9e442d92dcd9ee73a557428cfc336b55cbd533',
 
   # When changing these, also update the svn revisions in deps_revisions.gni
   'clang_format_revision': '96636aa0e9f047f17447f2d45a094d0b59ed7917',