call fetch-gn from git-sync-deps

https://skia.org/?cl=6994

Change-Id: Icac009bdef49f38ae7b8f082ffda6408481a03cd
Reviewed-on: https://skia-review.googlesource.com/6994
Reviewed-by: Hal Canary <halcanary@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
diff --git a/site/user/build.md b/site/user/build.md
index 52bc92b..9e17354 100644
--- a/site/user/build.md
+++ b/site/user/build.md
@@ -19,10 +19,9 @@
     bin/gn gen out/Static --args='is_official_build=true'
     bin/gn gen out/Shared --args='is_official_build=true is_component_build=true'
 
-If you find you don't have `bin/gn`, make sure you've run these steps.
+If you find you don't have `bin/gn`, make sure you've run
 
     python tools/git-sync-deps
-    python bin/fetch-gn
 
 GN allows fine-grained settings for developers and special situations.
 
diff --git a/site/user/download.md b/site/user/download.md
index febdf25..75a53da 100644
--- a/site/user/download.md
+++ b/site/user/download.md
@@ -24,7 +24,6 @@
     git clone https://skia.googlesource.com/skia.git
     cd skia
     python tools/git-sync-deps
-    python bin/fetch-gn
 
 Getting started with Skia
 -------------------------
diff --git a/tools/git-sync-deps b/tools/git-sync-deps
index e13ce88..2ff3427 100755
--- a/tools/git-sync-deps
+++ b/tools/git-sync-deps
@@ -223,6 +223,7 @@
     return 1
 
   git_sync_deps(deps_file_path, argv, verbose)
+  subprocess.check_call([sys.executable, 'bin/fetch-gn'])
   return 0