Use the Clang plugin on Windows.

build/common.gypi

 # Copyright (c) 2012 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 2156 matching lines @@
       ['enable_resource_whitelist_generation==1 and OS!="win"', {
         'grit_rc_header_format': ['-h', '#define {textual_id} _Pragma("whitelisted_resource_{numeric_id}") {numeric_id}'],
       }],
       ['enable_resource_whitelist_generation==1 and OS=="win"', {
         'grit_rc_header_format': ['-h', '#define {textual_id} __pragma(message("whitelisted_resource_{numeric_id}")) {numeric_id}'],
       }],
       ['enable_mdns==1 or OS=="mac"', {
         'grit_defines': ['-D', 'enable_service_discovery'],
         'enable_service_discovery%': 1
       }],
-      ['clang_use_chrome_plugins==1 and OS!="win"', {
+      ['clang_use_chrome_plugins==1', {
         'variables': {
           'conditions': [
-            ['OS=="mac" or OS=="ios"', {
-              'clang_lib_path%': '<!(cd <(DEPTH) && pwd -P)/third_party/llvm-build/Release+Asserts/lib/libFindBadConstructs.dylib',
-            }, { # OS != "mac" or OS != "ios"
-              'clang_lib_path%': '<!(cd <(DEPTH) && pwd -P)/third_party/llvm-build/Release+Asserts/lib/libFindBadConstructs.so',
-            }],
+            ['OS!="win"', {
+              'conditions': [
+                ['OS=="mac" or OS=="ios"', {
+                  'clang_lib_path%': '<!(cd <(DEPTH) && pwd -P)/third_party/llvm-build/Release+Asserts/lib/libFindBadConstructs.dylib',
+                }, { # OS != "mac" or OS != "ios"
+                  'clang_lib_path%': '<!(cd <(DEPTH) && pwd -P)/third_party/llvm-build/Release+Asserts/lib/libFindBadConstructs.so',
+                }],
+              ],
+              'clang_dynlib_flags%': '-Xclang -load -Xclang <(clang_lib_path) ',
+            }, { # OS == "win"
+              'clang_dynlib_flags%': '',

[hans, 2015/04/11 12:00:30]

Probably worth a comment that the plugins are linked in on Windows, so no need
to load them dynamically.

[dcheng, 2015/04/11 19:27:24]

Yeah, that's a good idea. Done.

+            }]
           ],
         },
         # If you change these, also change build/config/clang/BUILD.gn.
         'clang_chrome_plugins_flags%':
-          '-Xclang -load -Xclang <(clang_lib_path)'
-          ' -Xclang -add-plugin -Xclang find-bad-constructs',
+          '<(clang_dynlib_flags)'
+          '-Xclang -add-plugin -Xclang find-bad-constructs',
       }],
       ['asan==1 or msan==1 or lsan==1 or tsan==1', {
         'clang%': 1,
         'use_allocator%': 'none',
         'use_sanitizer_options%': 1,
         # Disable ICF in the linker to avoid debug info loss.
         'gold_icf_level%': 'none',
       }],
       ['asan==1 and OS=="linux" and chromeos==0', {
         'use_custom_libcxx%': 1,
@@ skipping 32 matching lines @@
             # 32-bit Clang is unsupported.  It may not build.  Put your 32-bit
             # Clang in this directory at your own risk if needed for some
             # purpose (e.g. to compare 32-bit and 64-bit behavior like memory
             # usage).  Any failure by this compiler should not close the tree.
             'make_clang_dir%': 'third_party/llvm-allocated-type/Linux_ia32',
           }],
         ],
       }],
 
       ['OS=="win"', {
-        # The Clang plugins don't currently work on Windows.
+        # The Blink GC plugin doesn't currently work on Windows.
         # TODO(hans): One day, this will work. (crbug.com/82385)
-        'clang_use_chrome_plugins%': 0,
+        'blink_gc_plugin%': 0,
       }],
 
       # On valgrind bots, override the optimizer settings so we don't inline too
       # much and make the stacks harder to figure out.
       #
       # TODO(rnk): Kill off variables that no one else uses and just implement
       # them under a build_for_tool== condition.
       ['build_for_tool=="memcheck" or build_for_tool=="tsan"', {
         # gcc flags
         'mac_debug_optimization': '1',
@@ skipping 3369 matching lines @@
               },
             }],
             ['clang==1 and target_arch=="ia32"', {
               'VCCLCompilerTool': {
                 'WarnAsError': 'false',
                 'AdditionalOptions': [
                   '/fallback',
                 ],
               },
             }],
+            ['clang==1 and clang_use_chrome_plugins==1', {
+              'VCCLCompilerTool': {
+                'AdditionalOptions': [
+                  '<@(clang_chrome_plugins_flags)',
+                ],
+              },
+            }],
           ],
         },
       },
     }],
     ['disable_nacl==1', {
       'target_defaults': {
         'defines': [
           'DISABLE_NACL',
         ],
       },
@@ skipping 458 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }