[web tests] Add specifier declarations in the heading

This CL adds the specifier declaration heading for the new test
expectations format. We want to make sure the expectations files are
backwards compatible with both blinkpy's and typ's expectations parsers.

Bug: chromium:986447
Change-Id: I96aebbe97f22a092a2f0767ca9510656070bb4e9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1967424
Reviewed-by: Robert Ma <[email protected]>
Commit-Queue: Robert Ma <[email protected]>
Cr-Commit-Position: refs/heads/master@{#725231}
diff --git a/third_party/blink/web_tests/W3CImportExpectations b/third_party/blink/web_tests/W3CImportExpectations
index 640928f..3ca5683 100644
--- a/third_party/blink/web_tests/W3CImportExpectations
+++ b/third_party/blink/web_tests/W3CImportExpectations
@@ -1,3 +1,8 @@
+# tags: [ Android Fuchsia IOS IOS12.2 IOS13.0 Linux Mac Mac10.10 Mac10.11 Mac10.12 Retina
+#         Mac10.13 Win Win7 Win10 ]
+# tags: [ Release Debug ]
+# results: [ Timeout Crash Pass Failure Slow Skip ]
+
 # This file controls which subdirectories of the w3c test repos we import.
 #
 # This file acts as a blacklist; directories and files not listed here will