Allow redirects for requests that require preflight.

third_party/WebKit/Source/core/loader/DocumentThreadableLoader.cpp

Index: third_party/WebKit/Source/core/loader/DocumentThreadableLoader.cpp
diff --git a/third_party/WebKit/Source/core/loader/DocumentThreadableLoader.cpp b/third_party/WebKit/Source/core/loader/DocumentThreadableLoader.cpp
index b98a47d5d7b4b8a63946e9f1ee0907c199c44183..848fb5d92eb790f7aacecc0d128142e97567673a 100644
--- a/third_party/WebKit/Source/core/loader/DocumentThreadableLoader.cpp
+++ b/third_party/WebKit/Source/core/loader/DocumentThreadableLoader.cpp
@@ -161,7 +161,6 @@ DocumentThreadableLoader::DocumentThreadableLoader(
       m_forceDoNotAllowStoredCredentials(false),
       m_securityOrigin(m_resourceLoaderOptions.securityOrigin),
       m_sameOriginRequest(false),
-      m_crossOriginNonSimpleRequest(false),
       m_isUsingDataConsumerHandle(false),
       m_async(blockingBehavior == LoadAsynchronously),
       m_requestContext(WebURLRequest::RequestContextUnspecified),
@@ -374,7 +373,6 @@ void DocumentThreadableLoader::makeCrossOriginAccessRequest(
     }
     loadRequest(crossOriginRequest, crossOriginOptions);
   } else {
-    m_crossOriginNonSimpleRequest = true;
     // Do not set the Origin header for preflight requests.
     updateRequestForAccessControl(crossOriginRequest, 0,
                                   effectiveAllowCredentials());
@@ -564,16 +562,8 @@ bool DocumentThreadableLoader::redirectReceived(
   bool allowRedirect = false;
   String accessControlErrorDescription;
 

[yhirano, 2016/10/27 06:19:44]

The preflight request (not a request w/preflight) shouldn't follow redirect,
right?

[Jack Bates, 2016/11/03 17:22:03]

Right. I confirm that if you try to redirect the preflight itself, Chromium
correctly raises a network error, both before and after this CL.

-  if (m_crossOriginNonSimpleRequest) {
-    // Non-simple cross origin requests (both preflight and actual one) are not
-    // allowed to follow redirect.
-    accessControlErrorDescription =
-        "Redirect from '" + redirectResponse.url().getString() + "' to '" +
-        request.url().getString() +
-        "' has been blocked by CORS policy: Request requires preflight, which "
-        "is disallowed to follow cross-origin redirect.";
-  } else if (!CrossOriginAccessControl::isLegalRedirectLocation(
-                 request.url(), accessControlErrorDescription)) {
+  if (!CrossOriginAccessControl::isLegalRedirectLocation(
+          request.url(), accessControlErrorDescription)) {
     accessControlErrorDescription =
         "Redirect from '" + redirectResponse.url().getString() +
         "' has been blocked by CORS policy: " + accessControlErrorDescription;