Whitelist environment variables used from Official chrome builds

pylib/gyp/msvs_emulation.py

Index: pylib/gyp/msvs_emulation.py
diff --git a/pylib/gyp/msvs_emulation.py b/pylib/gyp/msvs_emulation.py
index 6428fced00552e07ffa271dd0509047308d0cf79..1f59a6e587990c2a95646500623837a102725613 100644
--- a/pylib/gyp/msvs_emulation.py
+++ b/pylib/gyp/msvs_emulation.py
@@ -830,7 +830,7 @@ def _ExtractImportantEnvironment(output_of_set):
   """Extracts environment variables required for the toolchain to run from
   a textual dump output by the cmd.exe 'set' command."""
   envvars_to_save = (
-      'goma_.*', # TODO(scottmg): This is ugly, but needed for goma.
+      'goma_.*',  # TODO(scottmg): This is ugly, but needed for goma.
       'include',
       'lib',
       'libpath',
@@ -839,6 +839,11 @@ def _ExtractImportantEnvironment(output_of_set):
       'systemroot',
       'temp',
       'tmp',
+
+      # Needed to pass through some chrome flags.
+      # http://crbug.com/333738.
+      'chrom.*',
+      'official_build',
       )
   env = {}
   for line in output_of_set.splitlines():