Support clang-cl build on Windows.

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 300 matching lines @@
           }, {
             'ExceptionHandling': '0',
           }],
           ['target_arch=="x64"', {
             # 64-bit warnings need to be resolved.
             # https://code.google.com/p/pdfium/issues/detail?id=101
             'WarnAsError': 'false',
           }, {
             'WarnAsError': 'true',
           }],
+          ['clang==1', {
+            'AdditionalOptions': [
+              # Don't warn about unused function parameters.
+              # (This is also used on other platforms.)
+              '-Wno-unused-parameter',
+              # Don't warn about the "struct foo f = {0};" initialization
+              # pattern.
+              '-Wno-missing-field-initializers',
+
+              # Many files use intrinsics without including this header.
+              # TODO(hans): Fix those files, or move this to sub-GYPs.
+              '/FIIntrin.h',
+
+              # TODO(hans): Make this list shorter eventually, http://crbug.com/504657
+              '-Qunused-arguments',  # http://crbug.com/504658
+              '-Wno-microsoft-enum-value',  # http://crbug.com/505296
+              '-Wno-unknown-pragmas',  # http://crbug.com/505314
+              '-Wno-microsoft-cast',  # http://crbug.com/550065
+
+              # TODO(ochang): Fix these properly eventually.
+              '-Wno-inconsistent-missing-override',
+            ],
+          }],
+          ['clang==1 and MSVS_VERSION == "2013"', {
+            'VCCLCompilerTool': {
+              'AdditionalOptions': [
+                '-fmsc-version=1800',
+              ],
+            },
+          }],
+          ['clang==1 and MSVS_VERSION == "2015"', {
+            'VCCLCompilerTool': {
+              'AdditionalOptions': [
+                '-fmsc-version=1900',
+              ],
+            },
+          }],
         ],
       },
       'VCLibrarianTool': {
         'AdditionalOptions': ['/ignore:4221'],
       },
       'VCLinkerTool': {
         'GenerateDebugInformation': 'true',
         'LinkIncremental': '1',
         # SubSystem values:
         #   0 == not set
@@ skipping 116 matching lines @@
     ['OS=="linux" or OS=="mac"', {
       'conditions': [
         ['clang==1', {
           'make_global_settings': [
             ['CC', '<(clang_dir)/bin/clang'],
             ['CXX', '<(clang_dir)/bin/clang++'],
           ],
         }],
       ],
     }],  # OS=="linux" or OS=="mac"
+    ['OS=="win"', {
+      'conditions': [
+        ['clang==1', {
+          'make_global_settings': [
+            ['CC', '<(clang_dir)/bin/clang-cl'],
+          ],
+        }],
+      ],
+    }],  # OS=="win"
     ["use_goma==1", {
       'make_global_settings': [
         ['CC_wrapper', '<(gomadir)/gomacc'],
         ['CXX_wrapper', '<(gomadir)/gomacc'],
       ],
     }],  # use_goma==1
   ],
 }