Scripts to upload and update the mac toolchain.

DEPS

Index: DEPS
diff --git a/DEPS b/DEPS
index 54e3900469dc1b03ab65f75c0021f6ffe2e33525..3a9fec490f97475b7d43e02c436a8b90048ff0ef 100644
--- a/DEPS
+++ b/DEPS
@@ -598,6 +598,12 @@ hooks = [
     'pattern': '.',
     'action': ['python', 'src/build/vs_toolchain.py', 'update'],
   },
+  {
+    # Update the Mac toolchain if necessary.
+    'name': 'mac_toolchain',
+    'pattern': '.',
+    'action': ['python', 'src/build/mac_toolchain.py'],
+  },
   # Pull binutils for linux, enabled debug fission for faster linking /
   # debugging when used with clang on Ubuntu Precise.
   # https://code.google.com/p/chromium/issues/detail?id=352046