Refactor landmines.py so that it can be used downstream.

build/landmine_utils.py

Index: build/landmine_utils.py
diff --git a/build/landmine_utils.py b/build/landmine_utils.py
new file mode 100644
index 0000000000000000000000000000000000000000..3612bf0119c09d0418d80a99d0edf6537ed8f0fe
--- /dev/null
+++ b/build/landmine_utils.py
@@ -0,0 +1,114 @@
+# Copyright (c) 2013 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+
+import functools
+import logging
+import os
+import shlex
+import sys
+
+
+def memoize(default=None):
+  """This decorator caches the return value of a parameterless pure function"""
+  def memoizer(func):
+    val = []
+    @functools.wraps(func)
+    def inner():
+      if not val:
+        ret = func()
+        val.append(ret if ret is not None else default)
+        if logging.getLogger().isEnabledFor(logging.INFO):
+          print '%s -> %r' % (func.__name__, val[0])
+      return val[0]
+    return inner
+  return memoizer
+
+
+@memoize()
+def IsWindows():
+  return sys.platform in ['win32', 'cygwin']
+
+
+@memoize()
+def IsLinux():
+  return sys.platform.startswith('linux')
+
+
+@memoize()
+def IsMac():
+  return sys.platform == 'darwin'
+
+
+@memoize()
+def gyp_defines():
+  """Parses and returns GYP_DEFINES env var as a dictionary."""
+  return dict(arg.split('=', 1)
+      for arg in shlex.split(os.environ.get('GYP_DEFINES', '')))
+
+@memoize()
+def gyp_msvs_version():
+  return os.environ.get('GYP_MSVS_VERSION', '')
+
+@memoize()
+def distributor():
+  """
+  Returns a string which is the distributed build engine in use (if any).
+  Possible values: 'goma', 'ib', ''
+  """
+  if 'goma' in gyp_defines():
+    return 'goma'
+  elif IsWindows():
+    if 'CHROME_HEADLESS' in os.environ:
+      return 'ib' # use (win and !goma and headless) as approximation of ib
+
+
+@memoize()
+def platform():
+  """
+  Returns a string representing the platform this build is targetted for.
+  Possible values: 'win', 'mac', 'linux', 'ios', 'android'
+  """
+  if 'OS' in gyp_defines():
+    if 'android' in gyp_defines()['OS']:
+      return 'android'
+    else:
+      return gyp_defines()['OS']
+  elif IsWindows():
+    return 'win'
+  elif IsLinux():
+    return 'linux'
+  else:
+    return 'mac'
+
+
+@memoize()
+def builder():
+  """
+  Returns a string representing the build engine (not compiler) to use.
+  Possible values: 'make', 'ninja', 'xcode', 'msvs', 'scons'
+  """
+  if 'GYP_GENERATORS' in os.environ:
+    # for simplicity, only support the first explicit generator
+    generator = os.environ['GYP_GENERATORS'].split(',')[0]
+    if generator.endswith('-android'):
+      return generator.split('-')[0]
+    elif generator.endswith('-ninja'):
+      return 'ninja'
+    else:
+      return generator
+  else:
+    if platform() == 'android':
+      # Good enough for now? Do any android bots use make?
+      return 'ninja'
+    elif platform() == 'ios':
+      return 'xcode'
+    elif IsWindows():
+      return 'msvs'
+    elif IsLinux():
+      return 'ninja'
+    elif IsMac():
+      return 'xcode'
+    else:
+      assert False, 'Don\'t know what builder we\'re using!'