OOR-CORS: CORS-preflight requests do not need to have "Save-Data" header

Currently ServiceWorkerBrowserTest.CrossOriginFetchWithSaveData checks
if CORS-preflight requests have "Save-Data" header. This is existing
behavior, but new CORS stack does not add the "Save-Data" header for the
CORS-preflight. In terms of the fetch spec, it will be better not to
have the header in the preflight request.

Bug: 907389
Change-Id: Ic6906f5a9ce270a403b7be6f48274f78d2fce546
Reviewed-on: https://chromium-review.googlesource.com/c/1345685Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Commit-Queue: Takashi Toyoshima <toyoshim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610295}

content/browser/service_worker/service_worker_browsertest.cc

@@ -278,10 +278,17 @@ VerifySaveDataHeaderNotInRequest(const net::test_server::HttpRequest& request) {
 std::unique_ptr<net::test_server::HttpResponse>
 VerifySaveDataNotInAccessControlRequestHeader(
     const net::test_server::HttpRequest& request) {
-  // Save-Data should be present.
-  auto it = request.headers.find("Save-Data");
-  EXPECT_NE(request.headers.end(), it);
-  EXPECT_EQ("on", it->second);
+  if (base::FeatureList::IsEnabled(network::features::kOutOfBlinkCors)) {
+    // 'Save-Data' is not expected to be in the CORS preflight request.
+    auto it = request.headers.find("Save-Data");
+    EXPECT_EQ(request.headers.end(), it);
+  } else {
+    // The legacy code path appends 'Save-Data' header regardless of CORS
+    // preflight just because it can not be distinguished.
+    auto it = request.headers.find("Save-Data");
+    EXPECT_NE(request.headers.end(), it);
+    EXPECT_EQ("on", it->second);
+  }
 
   std::unique_ptr<net::test_server::BasicHttpResponse> http_response(
       new net::test_server::BasicHttpResponse());