Scripts to upload and update the mac toolchain.

DEPS

Index: DEPS
diff --git a/DEPS b/DEPS
index 8123fac0cadcfce63ecc4338ff7d04cab316a330..ced8ded773ae5d56acf88baa7441d628bfaf0a10 100644
--- a/DEPS
+++ b/DEPS
@@ -616,6 +616,12 @@ 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