Allow Win64 build of base library even in a Win32 build.

third_party/modp_b64/modp_b64.gyp

 # Copyright (c) 2009 The Chromium Authors. 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': 'modp_b64',
       'type': 'static_library',
       'toolsets': ['host', 'target'],
       'sources': [
         'modp_b64.cc',
         'modp_b64.h',
         'modp_b64_data.h',
       ],
       'include_dirs': [
         '../..',
       ],
     },
   ],
+  'conditions': [
+    ['OS == "win" and target_arch=="ia32"', {
+      # Even if we are building the browser for Win32, we need a few modules
+      # to be built for Win64, and this is a prerequsite.
+      'targets': [
+        {
+          'target_name': 'modp_b64_win64',
+          'type': 'static_library',
+          # We can't use dynamic_annotations target for win64 build since it is
+          # a 32-bit library.
+          'include_dirs': [
+            '../..',
+          ],
+          'sources': [
+            'modp_b64.cc',
+            'modp_b64.h',
+            'modp_b64_data.h',
+          ],
+          'configurations': {
+            'Common_Base': {
+              'msvs_target_platform': 'x64',
+            },
+          },
+        },
+      ],
+    }],
+  ],
 }