Roll GN from 972ed755 to 152c5144

Main purpose of this roll is to confirm that GN built on Xenial
by os upgrade in
https://gn.googlesource.com/gn.git/+/431bbf510dec8e10f607f7fff3f80a1ae84a737f
works on Trusty builder.

https://gn.googlesource.com/gn.git/+log/972ed755..152c5144

152c5144 Update and add metadata documentation
579b5b39 Move 'rust_example' to the toplevel 'examples' folder
61be3f2e Fix desc to handle single-value outputs correctly
bf27729d [rust] Update RustTargetGenerator to not duplicate work
4c0c60eb Move examples to toplevel, document better.
c4a88ac9 Allow crate type to be set on all Rust targets
23d22bca [docs] : fix typo 'then' => 'they' and re-generate 'reference.md'
3b5fa962 [docs] : add Markdown format for '--time'
9edc6c08 [docs] : clean up cross_compiles.md
d3304fbb [docs] : fix typo sone => some
fe0c6bbb Write depfile for non-C-like tools
f898ccf7 Fix linking deps propagation
445ac323 [docs] GN can tell empty lists from non empty lists
3ddcc49a Fix build with GCC on FreeBSD

Bug: 981741
Change-Id: I062d6b21d3955cd0a2773321b4f68056972f8950
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1714681Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#680112}

DEPS

@@ -298,7 +298,7 @@ vars = {
   # revisions.
 
   # GN CIPD package version.
-  'gn_version': 'git_revision:972ed755f8e6d31cae9ba15fcd08136ae1a7886f',
+  'gn_version': 'git_revision:152c5144ceed9592c20f0c8fd55769646077569b',
 
   # 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:972ed755f8e6d31cae9ba15fcd08136ae1a7886f',
+  'gn_version': 'git_revision:152c5144ceed9592c20f0c8fd55769646077569b',
 
   # When changing these, also update the svn revisions in deps_revisions.gni
   'clang_format_revision': '96636aa0e9f047f17447f2d45a094d0b59ed7917',