Make Clang's update.py use the Win toolchain under depot_tools if available

DEPS

 # This file is automatically processed to create .DEPS.git which is the file
 # that gclient uses under git.
 #
 # See http://code.google.com/p/chromium/wiki/UsingGit
 #
 # To test manually, run:
 #   python tools/deps2git/deps2git.py -o .DEPS.git -w <gclientdir>
 # where <gcliendir> is the absolute path to the directory containing the
 # .gclient file (the parent of 'src').
 #
@@ skipping 578 matching lines @@
     # Same as above, but for 32-bit Linux.
     'name': 'sysroot',
     'pattern': '.',
     'action': [
         'python',
         'src/chrome/installer/linux/sysroot_scripts/install-debian.wheezy.sysroot.py',
         '--linux-only',
         '--arch=i386'],
   },
   {
-    # Pull clang if on Mac or clang is requested via GYP_DEFINES.
-    'name': 'clang',
-    'pattern': '.',
-    'action': ['python', 'src/tools/clang/scripts/update.py', '--if-needed'],
-  },
-  {
     # Update the Windows toolchain if necessary.
     'name': 'win_toolchain',
     'pattern': '.',
     'action': ['python', 'src/build/vs_toolchain.py', 'update'],
   },
   {
+    # Pull clang if needed or requested via GYP_DEFINES.
+    # Note: On Win, this should run after win_toolchain, as it may use it.
+    'name': 'clang',
+    'pattern': '.',
+    'action': ['python', 'src/tools/clang/scripts/update.py', '--if-needed'],
+  },
+  {
     # Update LASTCHANGE. This is also run by export_tarball.py in
     # src/tools/export_tarball - please keep them in sync.
     'name': 'lastchange',
     'pattern': '.',
     'action': ['python', 'src/build/util/lastchange.py',
                '-o', 'src/build/util/LASTCHANGE'],
   },
   {
     # Update LASTCHANGE.blink. This is also run by export_tarball.py in
     # src/tools/export_tarball - please keep them in sync.
@@ skipping 171 matching lines @@
     # corresponding .py files have already been deleted.
     'name': 'remove_stale_pyc_files',
     'pattern': 'src/tools/.*\\.py',
     'action': [
         'python',
         'src/tools/remove_stale_pyc_files.py',
         'src/tools',
     ],
   },
 ]