Leave out empty-valued Access-Control-Request-Headers: on preflights.

third_party/WebKit/LayoutTests/http/tests/fetch/script-tests/thorough/cors-preflight2.js

Index: third_party/WebKit/LayoutTests/http/tests/fetch/script-tests/thorough/cors-preflight2.js
diff --git a/third_party/WebKit/LayoutTests/http/tests/fetch/script-tests/thorough/cors-preflight2.js b/third_party/WebKit/LayoutTests/http/tests/fetch/script-tests/thorough/cors-preflight2.js
index 675cd6bb217e62f44187127d775b0c04293cf221..3fdafc3888228749800a00fc821a30a05f9bc78b 100644
--- a/third_party/WebKit/LayoutTests/http/tests/fetch/script-tests/thorough/cors-preflight2.js
+++ b/third_party/WebKit/LayoutTests/http/tests/fetch/script-tests/thorough/cors-preflight2.js
@@ -167,6 +167,15 @@ var TEST_TARGETS = [];
        '&PACRHeaders=x-serviceworker-test&PreflightTest=200',
        [fetchResolved, noContentLength, noServerHeader, hasBody, typeCors],
        [checkMethod, hasCustomHeader]],
+
+      // Verify that Access-Control-Request-Headers: is not present in preflight
+      // if its value is the empty list - https://crbug.com/633729
+      [OTHER_BASE_URL + 'mode=cors&credentials=same-origin&method=' + method +
+       '&headers=SAFE&ACAOrigin=*&PACAOrigin=*&PACAMethods=' + method +
+       '&PACRHeaders=missing&PACRMethod=' + method + '&PreflightTest=200',
+       [fetchResolved, noContentLength, noServerHeader, hasBody, typeCors],
+       [checkMethod]],
+
       // Test Access-Control-Request-Headers is sorted https://crbug.com/452391
       [OTHER_BASE_URL + 'mode=cors&credentials=same-origin&method=' + method +
        '&headers=CUSTOM2&ACAOrigin=*&PACAOrigin=*&PACAMethods=' + method +