Don't #define snprintf in VS 2015 builds.

The function snprintf is not available in Visual Studio prior to VS
2015. In some places this omission is dealt with with a #define to map
snprintf to _snprintf. This was never a good idea (_snprintf doesn't
guarantee null-termination) and with VS 2015 it is not even legal.

This change conditionally disables one instance of this remapping.

The build errors that occur without this change are:

stdio.h(1926): warning C4005: 'snprintf': macro redefinition
stdio.h(1926): note: command-line arguments:  see previous
definition of 'snprintf'
stdio.h(1929): fatal error C1189: #error:  Macro definition of
snprintf conflicts with Standard Library function declaration

R=scottmg@chromium.org
BUG=440500

Review URL: https://codereview.chromium.org/1069433002

Cr-Commit-Position: refs/heads/master@{#324157}

content/content_shell.gypi

@@ -743,9 +743,14 @@
           'dependencies': [ '../build/linux/system.gyp:x11' ],
         }],
         ['OS=="win"', {
-          'defines': [
-            # This seems like a hack, but this is what Safari Win does.
-            'snprintf=_snprintf',
+          'conditions': [
+            ['MSVS_VERSION < "2015"', {
+              'defines': [
+                # This seems like a hack, but this is what Safari Win does.
+                # Luckily it is no longer needed/allowed with VS 2015.
+                'snprintf=_snprintf',
+              ],
+            }],
           ],
           'sources': [
             'shell/tools/plugin/win/TestNetscapePlugin.def',

third_party/libexif/libexif.gyp

@@ -83,9 +83,16 @@
               'sources': [
                 'libexif.def',
               ],
+              'conditions': [
+                ['MSVS_VERSION < "2015"', {
+                  'defines': [
+                    # This seems like a hack, but this is what Safari Win does.
+                    # Luckily it is no longer needed/allowed with VS 2015.
+                    'snprintf=_snprintf',
+                  ],
+                }],
+              ],
               'defines': [
-                # This seems like a hack, but this is what WebKit Win does.
-                'snprintf=_snprintf',
                 'inline=__inline',
               ],
               'msvs_disabled_warnings': [