Fix pdfium standalone to compile with VS 2015.

build/standalone.gypi

 # Copyright 2014 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.
 
 # Definitions to be used when building stand-alone PDFium binaries.
 
 {
   'variables': {
     'component%': 'static_library',
     'clang%': 0,
@@ skipping 145 matching lines @@
     ],
     'ldflags': [
       '-pthread',
     ],
     'msvs_cygwin_dirs': ['<(DEPTH)/v8/third_party/cygwin'],
     'msvs_configuration_attributes': {
       'OutputDirectory': '<(DEPTH)\\build\\$(ConfigurationName)',
       'IntermediateDirectory': '$(OutDir)\\obj\\$(ProjectName)',
       'CharacterSet': '1',
     },
-    'msvs_disabled_warnings': [4800, 4996],
+    'msvs_disabled_warnings': [4800, 4996, 4456, 4457, 4458, 4459, 4091],
+    # 4456, 4457, 4458, 4459 are variable shadowing warnings that are new in
+    # VS2015.
+    # C4091: 'typedef ': ignored on left of 'X' when no variable is
+    #                    declared.
+    # This happens in a number of Windows headers with VS 2015.
     'msvs_settings': {
       'VCCLCompilerTool': {
         'MinimalRebuild': 'false',
         'BufferSecurityCheck': 'true',
         'EnableFunctionLevelLinking': 'true',
         'RuntimeTypeInfo': 'false',
         'WarningLevel': '3',
         'DebugInformationFormat': '3',
         'Detect64BitPortabilityProblems': 'false',
         'conditions': [
@@ skipping 91 matching lines @@
           'V8_USE_EXTERNAL_STARTUP_DATA',
         ],
       },
     }],  # v8_use_external_startup_data==1
   ],
   'xcode_settings': {
     # See comment in Chromium's common.gypi for why this is needed.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   }
 }