Extracts CT DNS test utilities into a standalone class

components/certificate_transparency.gypi

Index: components/certificate_transparency.gypi
diff --git a/components/certificate_transparency.gypi b/components/certificate_transparency.gypi
index cfdfe4b799e32c31682d0323acea3ef7d603fb7e..cde58f558faeeff1ebb71f46f1ca897833f061cb 100644
--- a/components/certificate_transparency.gypi
+++ b/components/certificate_transparency.gypi
@@ -35,6 +35,24 @@
         'certificate_transparency/tree_state_tracker.h',
         'certificate_transparency/tree_state_tracker.cc',
       ],
-    }
+    },
+    {
+      # GN version: //components/certificate_transparency:test_support
+      'target_name': 'certificate_transparency_test_support',
+      'type': 'static_library',
+      'include_dirs': [
+        '..',
+      ],
+      'dependencies': [
+        '../base/base.gyp:base',
+        '../net/net.gyp:net',
+        '../net/net.gyp:net_test_support',
+        '../testing/gtest.gyp:gtest',
+      ],
+      'sources': [
+        'certificate_transparency/mock_log_dns_traffic.cc',
+        'certificate_transparency/mock_log_dns_traffic.h',
+      ],
+    },
   ],
 }