https://codereview.chromium.org/2106203002/diff/180001/build/vs_toolchain.py?context=25&column_width=80&tab_spaces=8 updated us to vs2015 update 3.

win_upload_clang fails with 

Checked out revision 281889.
Building bootstrap compiler
Traceback (most recent call last):
  File "E:\b\build\slave\win_upload_clang\build\src\tools\clang\scripts\update.py", line 909, in <module>
    sys.exit(main())
  File "E:\b\build\slave\win_upload_clang\build\src\tools\clang\scripts\update.py", line 905, in main
    return UpdateClang(args)
  File "E:\b\build\slave\win_upload_clang\build\src\tools\clang\scripts\update.py", line 518, in UpdateClang
    RunCommand(['cmake'] + bootstrap_args + [LLVM_DIR], msvc_arch='x64')
  File "E:\b\build\slave\win_upload_clang\build\src\tools\clang\scripts\update.py", line 210, in RunCommand
    command = GetVSVersion().SetupScript(msvc_arch) + ['&&'] + command
  File "E:\b\build\slave\win_upload_clang\build\src\tools\gyp\pylib\gyp\MSVSVersion.py", line 116, in SetupScript
    script_path)
Exception: E:\b\depot_tools\win_toolchain\vs_files\95ddda401ec5678f15eeed01d2bee08fcbc5ee97\VC\vcvarsall.bat is missing - make sure VC++ tools are installed.
Failed: ['E:\\b\\depot_tools\\python276_bin\\python.exe', 'E:\\b\\build\\slave\\win_upload_clang\\build\\src\\tools\\clang\\scripts\\update.py', '--bootstrap', '--force-local-build', '--run-tests']
step returned non-zero exit code: 1



That's the hash from the old toolchain; not sure why it's not using the new hash.


update.py does:


vs_version = None
def GetVSVersion():
  global vs_version
  if vs_version:
    return vs_version

  # Try using the toolchain in depot_tools.
  # This sets environment variables used by SelectVisualStudioVersion below.
  sys.path.append(os.path.join(CHROMIUM_DIR, 'build'))
  import vs_toolchain
  vs_toolchain.SetEnvironmentAndGetRuntimeDllDirs()

  # Use gyp to find the MSVS installation, either in depot_tools as per above,
  # or a system-wide installation otherwise.
  sys.path.append(os.path.join(CHROMIUM_DIR, 'tools', 'gyp', 'pylib'))
  import gyp.MSVSVersion
  vs_version = gyp.MSVSVersion.SelectVisualStudioVersion(
      vs_toolchain.GetVisualStudioVersion())
  return vs_version



Depending on gyp is probably a bad idea in the long run, but from glancing at it quickly it should probably still work.

(see win_upload_clang run on ps1 on https://codereview.chromium.org/2349183003 -- https://build.chromium.org/p/tryserver.chromium.win/builders/win_upload_clang/builds/104/steps/package%20clang/logs/stdio)