run cygwin mount setup in runhooks, and remove some references to it

build/win/setup_cygwin_mount.py

Index: build/win/setup_cygwin_mount.py
diff --git a/build/win/setup_cygwin_mount.py b/build/win/setup_cygwin_mount.py
new file mode 100644
index 0000000000000000000000000000000000000000..b797733bad35f125f114118b6ddc48ccfd63f381
--- /dev/null
+++ b/build/win/setup_cygwin_mount.py
@@ -0,0 +1,20 @@
+# Copyright (c) 2012 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 os
+import sys
+
+def main():
+  if len(sys.argv) != 2 or sys.argv[1] != '--win-only':
+    return 1
+  if 'win' in sys.platform:
+    self_dir = os.path.dirname(sys.argv[0])
+    mount_path = os.path.join(self_dir, "..\\..\\third_party\\cygwin")
+    batch_path = os.path.join(mount_path, "setup_mount.bat")
+    return os.system(os.path.normpath(batch_path) + ">nul")

[jam, 2012/01/28 00:06:57]

I suspect it'll be much faster to do the registry operations here than to run a
bat file which runs reg.exe a bunch of times. it'll also reduce the need to run
an external bat file which I can't imagine is fast.

but if you time it and this is really short, then ignore this.

[scottmg, 2012/01/28 00:20:09]

I get 0.34s. I'd lean towards not doing it so I don't break it (and since it's
during sync anyway), but I don't mind doing it if you think it's worth it.

+  return 0
+
+
+if __name__ == "__main__":
+  sys.exit(main())