Add test for multithreaded ActiveVerifier behavior.

base/base.gyp

Index: base/base.gyp
diff --git a/base/base.gyp b/base/base.gyp
index 5b20cfec9fd86d45ac2248d87fb312ea1a00d6c1..c4ed5c7f3b1e448332b58eff9068d077cb985077 100644
--- a/base/base.gyp
+++ b/base/base.gyp
@@ -699,6 +699,9 @@
           ],
         }],
         ['OS == "win"', {
+          'dependencies': [
+            'scoped_handle_test_dll'

[Nico, 2016/03/11 23:26:58]

...and in gyp you instead link base_unittests against this dll?

[Will Harris, 2016/03/12 00:00:01]

now it's a loadable_module it shouldn't do any kind of linking against
base_unittests.

+          ],
           'sources!': [
             'file_descriptor_shuffle_unittest.cc',
             'files/dir_reader_posix_unittest.cc',
@@ -1680,6 +1683,16 @@
             },
           },
         },
+        {
+          'target_name': 'scoped_handle_test_dll',
+          'type': 'shared_library',
+          'dependencies': [
+            'base',
+          ],
+          'sources': [
+            'win/scoped_handle_test_dll.cc',
+          ],
+        },
       ],
     }],
     ['test_isolation_mode != "noop"', {