[NoStatePrefetch] Do not send responses to renderer in prefetch mode.

content/child/web_url_request_util.cc

Index: content/child/web_url_request_util.cc
diff --git a/content/child/web_url_request_util.cc b/content/child/web_url_request_util.cc
index e23e5b7bea1889207fe62a34ea84cefd73dba05f..85c0ef1857fd587f2f3155a0823aa40cd3861e5f 100644
--- a/content/child/web_url_request_util.cc
+++ b/content/child/web_url_request_util.cc
@@ -11,6 +11,7 @@
 
 #include "base/logging.h"
 #include "base/strings/string_util.h"
+#include "content/child/request_extra_data.h"
 #include "net/base/load_flags.h"
 #include "net/base/net_errors.h"
 #include "third_party/WebKit/public/platform/FilePathConversion.h"
@@ -216,6 +217,13 @@ int GetLoadFlagsForWebURLRequest(const blink::WebURLRequest& request) {
   if (!request.allowStoredCredentials())
     load_flags |= net::LOAD_DO_NOT_SEND_AUTH_DATA;
 
+  if (request.getExtraData()) {
+    RequestExtraData* extra_data =
+        static_cast<RequestExtraData*>(request.getExtraData());
+    if (extra_data->is_prefetch())
+      load_flags |= net::LOAD_PREFETCH;

[mmenke, 2016/08/25 19:41:09]

Wait....This looks problematic.  Could we remove this part of the CL?  It looks
to me like the LOAD_PREFETCH check in net/ fails to distinguish between CORS and
non-CORS requests, which seems bad to me.

If we do a prefetch in a way that sends cookies, and don't use a request, and
then another page requests the resource in a way that does not, it can get the
response with the cookies, even if there's a "Vary: Cookie" header, which seems
problematic.  I could be missing some protection against this, but I'm not
seeing one.

[droger, 2016/08/30 08:47:56]

As discussed offline, this has been resolved (see bug https://crbug.com/641103).

+  }
+
   return load_flags;
 }