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

DEPS

 vars = {
   # Use this googlecode_url variable only if there is an internal mirror for it.
   # If you do not know, use the full path while defining your new deps entry.
   "googlecode_url": "http://%s.googlecode.com/svn",
   "sourceforge_url": "http://%(repo)s.svn.sourceforge.net/svnroot/%(repo)s",
   "webkit_trunk": "http://svn.webkit.org/repository/webkit/trunk",
   "nacl_trunk": "http://src.chromium.org/native_client/trunk",
   "webkit_revision": "106131",
   "chromium_git": "http://git.chromium.org/git",
   "swig_revision": "69281",
@@ skipping 459 matching lines @@
     ],
   },
   {
     # Pull clang on mac. If nothing changed, or on non-mac platforms, this takes
     # zero seconds to run. If something changed, it downloads a prebuilt clang,
     # which takes ~20s, but clang speeds up builds by more than 20s.
     "pattern": ".",
     "action": ["python", "src/tools/clang/scripts/update.py", "--mac-only"],
   },
   {
+    # Update the cygwin mount on Windows.
+    "pattern": "."
+    "action": ["python", "src/build/win/setup_cygwin_mount.py", "--win-only"],
+  },
+  {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     "pattern": ".",
     "action": ["python", "src/build/gyp_chromium"],
   },
 ]