UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36

Steps to reproduce the problem:
1. fetch chromium source code
2. run gclient sync
3. observe script output

What is the expected behavior?
script goes through

What went wrong?
________ running 'download_from_google_storage --no_resume --platform=win32 --no_auth --bucket chromium-gn -s src/buildtools/win/gn.exe.sha1' in '/Users/jracle/Dev/chromium'
Traceback (most recent call last):
  File "/Users/jracle/Dev/depot_tools/gclient.py", line 2128, in <module>
    sys.exit(main(sys.argv[1:]))
  File "/Users/jracle/Dev/depot_tools/gclient.py", line 2114, in main
    return dispatcher.execute(OptionParser(), argv)
  File "/Users/jracle/Dev/depot_tools/subcommand.py", line 252, in execute
    return command(parser, args[1:])
  File "/Users/jracle/Dev/depot_tools/gclient.py", line 1876, in CMDsync
    ret = client.RunOnDeps('update', args)
  File "/Users/jracle/Dev/depot_tools/gclient.py", line 1371, in RunOnDeps
    self.RunHooksRecursively(self._options)
  File "/Users/jracle/Dev/depot_tools/gclient.py", line 921, in RunHooksRecursively
    hook, cwd=self.root.root_dir, always=True)
  File "/Users/jracle/Dev/depot_tools/gclient_utils.py", line 303, in CheckCallAndFilterAndHeader
    return CheckCallAndFilter(args, **kwargs)
  File "/Users/jracle/Dev/depot_tools/gclient_utils.py", line 498, in CheckCallAndFilter
    **kwargs)
  File "/Users/jracle/Dev/depot_tools/subprocess2.py", line 262, in __init__
    % (str(e), kwargs.get('cwd'), args[0]))

--> script tries to download gn for windows... but I'm on mac.

If I type manually following command :
download_from_google_storage --no_resume --platform=darwin --no_auth --bucket chromium-gn -s src/buildtools/mac/gn.sha1

Then gn is downloaded correctly. I can run "gn gen out/Default --ide=xcode" and start compiling, but then compilation fails (due to missing component ; I guess this is due to the fact that gclient sync was missing to run till-the-end)

ninja -C out/Debug/ -j 5 chrome
ninja: Entering directory `out/Debug/'
[62/27536] ACTION //chrome/browser/resources/md_downloads:vulcanize(//build/toolchain/mac:clang_x64)
FAILED: gen/chrome/browser/resources/md_downloads/vulcanized.html gen/chrome/browser/resources/md_downloads/crisper.js 
python ../../chrome/browser/resources/vulcanize_gn.py --host downloads --html_in_file downloads.html --html_out_file vulcanized.html --js_out_file crisper.js --input_type FOLDER --input ../../chrome/browser/resources/md_downloads --insert_in_head \<base\ href=chrome://downloads\> --out_folder gen/chrome/browser/resources/md_downloads --depfile gen/chrome/browser/resources/md_downloads/vulcanize.d
../../third_party/node/mac/node-darwin-x64/bin/node ../../third_party/node/node_modules/vulcanize/bin/vulcanize --exclude crisper.js --exclude chrome://resources/html/polymer.html --exclude web-animations-next-lite.min.js --exclude load_time_data.js --exclude strings.js --exclude text_defaults.css --exclude text_defaults_md.css --inline-css --inline-scripts --strip-comments --redirect "chrome://resources/cr_elements/|../../ui/webui/resources/cr_elements" --redirect "chrome://resources/css/|../../ui/webui/resources/css" --redirect "chrome://resources/html/|../../ui/webui/resources/html" --redirect "chrome://resources/js/|../../ui/webui/resources/js" --redirect "chrome://resources/polymer/v1_0/|../../third_party/polymer/v1_0/components-chromium" --out-request-list /Users/jracle/Dev/chromium/src/out/Debug/gen/chrome/browser/resources/md_downloads/request_list.txt --redirect "/|/Users/jracle/Dev/chromium/src/chrome/browser/resources/md_downloads" --redirect "chrome://downloads/|/Users/jracle/Dev/chromium/src/chrome/browser/resources/md_downloads" /downloads.html failed: /bin/sh: ../../third_party/node/mac/node-darwin-x64/bin/node: No such file or directory

Traceback (most recent call last):
  File "../../chrome/browser/resources/vulcanize_gn.py", line 220, in <module>
    main()
  File "../../chrome/browser/resources/vulcanize_gn.py", line 213, in main
    _vulcanize(vulcanize_input_folder, args)
  File "../../chrome/browser/resources/vulcanize_gn.py", line 153, in _vulcanize
    args.html_in_file)])
  File "../../chrome/browser/resources/vulcanize_gn.py", line 90, in _run_node
    raise
TypeError: exceptions must be old-style classes or derived from BaseException, not NoneType
[66/27536] ACTION //components/resources:about_credits(//build/toolchain/mac:clang_x64)
ninja: build stopped: subcommand failed.

Did this work before? N/A 

Chrome version: 56.0.2924.87  Channel: stable
OS Version: OS X 10.12.3
Flash Version: 

Attached my system report : I'm using new macbook pro with touchbar, latest mac os X with 10.12 SDK.

Can you triage issue ASAP please? thanks!