clang/win: Enable oilpan 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 2227 matching lines @@
           ['host_arch=="ia32"', {
             # 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 Blink GC plugin doesn't currently work on Windows.
-        # TODO(hans): One day, this will work. (crbug.com/82385)
-        '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',
         'mac_release_optimization': '1',
         'release_optimize': '1',
@@ skipping 3923 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',
   },
 }