Re-enable several MSVC warnings

pdfium.gyp

 # Copyright 2015 PDFium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'variables': {
     # TODO(thakis): Enable this, pdfium:29
     #'chromium_code': 1,
 
     'variables': {
@@ skipping 78 matching lines @@
       }],
       ['clang==1 and clang_use_pdfium_plugins==1', {
         'cflags': [
           '<@(clang_pdfium_plugins_flags)',
         ],
       }],
     ],
     'msvs_disabled_warnings': [
       4005, 4018, 4146, 4333, 4345, 4267,
       # TODO(thestig): Fix all instances, remove this, pdfium:29
-      4245, 4310, 4389, 4701, 4702, 4706,
+      4702,
     ],
     'variables': {
       'clang_warning_flags': [
         # TODO(thestig): Fix all instances, remove this, pdfium:29
         '-Wno-sign-compare',
       ],
       # Make sure Chromium's build/common.gypi doesn't re-add the flag on linux.
       'cflags_cc!': [ '-Wsign-compare' ],
     },
   },
@@ skipping 855 matching lines @@
             'fpdfsdk/include/fpdfxfa/fpdfxfa_app.h',
             'fpdfsdk/include/fpdfxfa/fpdfxfa_doc.h',
             'fpdfsdk/include/fpdfxfa/fpdfxfa_page.h',
             'fpdfsdk/include/fpdfxfa/fpdfxfa_util.h',
           ],
         },
       ]
     }],
   ]
 }