Revert of [build] Use MSVS 2015 by default.

DEPS

 # Note: The buildbots evaluate this file with CWD set to the parent
 # directory and assume that the root of the checkout is in ./v8/, so
 # all paths in here must match this assumption.
 
 vars = {
   "chromium_url": "https://chromium.googlesource.com",
 }
 
 deps = {
   "v8/build":
@@ skipping 245 matching lines @@
     'pattern': '\\.sha1',
     'action': [
         'python',
         'v8/third_party/instrumented_libraries/scripts/download_binaries.py',
     ],
   },
   {
     # Update the Windows toolchain if necessary.
     'name': 'win_toolchain',
     'pattern': '.',
-    'action': ['python', 'v8/build/vs_toolchain.py', 'update'],
+    'action': ['python', 'v8/gypfiles/vs_toolchain.py', 'update'],
   },
   # 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
   {
     'name': 'binutils',
     'pattern': 'v8/third_party/binutils',
     'action': [
         'python',
         'v8/third_party/binutils/download.py',
@@ skipping 12 matching lines @@
     'name': 'clang',
     'pattern': '.',
     'action': ['python', 'v8/tools/clang/scripts/update.py', '--if-needed'],
   },
   {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     "pattern": ".",
     "action": ["python", "v8/gypfiles/gyp_v8", "--running-as-hook"],
   },
 ]