win: 'EnableEnhancedInstructionSet': '5' now enables /arch:AVX2.

test/win/compiler-flags/enable-enhanced-instruction-set.gyp

 # Copyright (c) 2014 Google Inc. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'targets': [
     {
       'target_name': 'sse_extensions',
       'type': 'executable',
       'msvs_settings': {
@@ skipping 32 matching lines @@
           'type': 'executable',
           'msvs_settings': {
             'VCCLCompilerTool': {
               'EnableEnhancedInstructionSet': '4',  # NoExtensions
             }
           },
           'sources': ['enable-enhanced-instruction-set.cc'],
         },
       ],
     }],
+    ['MSVS_VERSION[0:4]>="2013"', {
+      'targets': [
+        {
+          'target_name': 'avx2_extensions',
+          'type': 'executable',
+          'msvs_settings': {
+            'VCCLCompilerTool': {
+              'EnableEnhancedInstructionSet': '5',  # AdvancedVectorExtensions2
+            }
+          },
+          'sources': ['enable-enhanced-instruction-set.cc'],
+        },
+      ],
+    }],
   ],
 }