Only import gyp when required in vs_toolchain.py.

build/vs_toolchain.py

Index: build/vs_toolchain.py
diff --git a/build/vs_toolchain.py b/build/vs_toolchain.py
index c5db1b249e40ff8df0986bad566df879563c2299..f325e5d74261575a665e80876c5a18f1fc7964a9 100755
--- a/build/vs_toolchain.py
+++ b/build/vs_toolchain.py
@@ -21,9 +21,6 @@ sys.path.insert(0, os.path.join(chrome_src, 'tools', 'gyp', 'pylib'))
 json_data_file = os.path.join(script_dir, 'win_toolchain.json')
 
 
-import gyp
-
-
 # Use MSVS2015 as the default toolchain.
 CURRENT_DEFAULT_TOOLCHAIN_VERSION = '2015'
 
@@ -64,6 +61,7 @@ def SetEnvironmentAndGetRuntimeDllDirs():
     # toolchain values in GYP_DEFINES, but don't want to override any
     # otheroptions.express
     # values there.
+    import gyp

[brucedawson, 2017/03/10 23:31:49]

Feels like the comment above applies to this line, which makes it slightly
confusing. Maybe add a comment about how this is to minimize the exposure to
gyp?

[Lei Zhang, 2017/03/10 23:43:07]

Done.

     gyp_defines_dict = gyp.NameValueListToDict(gyp.ShlexEnv('GYP_DEFINES'))
     gyp_defines_dict['windows_sdk_path'] = win_sdk
     os.environ['GYP_DEFINES'] = ' '.join('%s=%s' % (k, pipes.quote(str(v)))
@@ -171,12 +169,11 @@ def _VersionNumber():
   vs_version = GetVisualStudioVersion()
   if vs_version == '2013':
     return '120'
-  elif vs_version == '2015':
+  if vs_version == '2015':
     return '140'
-  elif vs_version == '2017':
+  if vs_version == '2017':
     return '150'
-  else:
-    raise ValueError('Unexpected GYP_MSVS_VERSION')
+  raise ValueError('Unexpected GYP_MSVS_VERSION')
 
 
 def _CopyRuntimeImpl(target, source, verbose=True):
@@ -343,8 +340,7 @@ def _GetDesiredVsToolchainHashes():
   if GetVisualStudioVersion() == '2015':
     # Update 3 final with patches with 10.0.14393.0 SDK.
     return ['d3cb0e37bdd120ad0ac4650b674b09e81be45616']
-  else:
-    return ['03a4e939cd325d6bc5216af41b92d02dda1366a6']
+  return ['03a4e939cd325d6bc5216af41b92d02dda1366a6']

[brucedawson, 2017/03/10 23:31:49]

This is going to conflict with another CL that I just uploaded:

https://codereview.chromium.org/2741783006/diff/1/build/vs_toolchain.py

We could race to the finish line, or you could incorporate part or all of my
change. It turns out that having a default case is a bad idea.

[Lei Zhang, 2017/03/10 23:33:15]

Please land your CL first. I'm not in any rush here.

 
 
 def ShouldUpdateToolchain():