Add ReferrerPolicy support to preload

third_party/WebKit/Source/platform/network/LinkHeaderTest.cpp

Index: third_party/WebKit/Source/platform/network/LinkHeaderTest.cpp
diff --git a/third_party/WebKit/Source/platform/network/LinkHeaderTest.cpp b/third_party/WebKit/Source/platform/network/LinkHeaderTest.cpp
index 4c23d31f1fc476bf79adeb54a81a096a1fbac716..5f18f3aa05094c754c5819d4499b548a3f771d8d 100644
--- a/third_party/WebKit/Source/platform/network/LinkHeaderTest.cpp
+++ b/third_party/WebKit/Source/platform/network/LinkHeaderTest.cpp
@@ -26,6 +26,7 @@ struct SingleTestCase {
   const char* rel;
   const char* as;
   const char* media;
+  const char* referrerPolicy;
 } singleTestCases[] = {
     {"</images/cat.jpg>; rel=prefetch", true, "/images/cat.jpg", "prefetch", "",
      ""},
@@ -150,6 +151,8 @@ struct SingleTestCase {
      "/images/cat.jpg", "prefetch", "", "(max-width: 5000px)"},
     {"</images/cat.jpg>; rel=prefetch;media=(max-width:5000px)", true,
      "/images/cat.jpg", "prefetch", "", "(max-width:5000px)"},
+    {"</images/cat.jpg>; rel=preload;referrerpolicy=somevalue", true,

[Mike West, 2016/10/23 05:25:46]

I guess this is a reasonable addition, but it needs to be specified somewhere.
We should probably also be taking the `referrer-policy` header into account
(which, again, is an argument for specifying the behavior somewhere :) ).

[Yoav Weiss, 2016/10/23 13:27:09]

I considered it as a "link-extension" defined in
https://tools.ietf.org/html/rfc5988#section-5 (Similar to what we do with `as`
and the way the `nopush` attribute is being used (even if browsers don't really
need to support it).

Do you think we need to define it (and other new attributes) explicitly? If so,
I'll be happy do that.

I assumed the header is being taken into account in the code that consumes that
header (as the document's referrer policy). A test wouldn't hurt tho 

+     "/images/cat.jpg", "preload", "", "", "somevalue"},

[Mike West, 2016/10/23 05:25:46]

I don't understand how this test works. You've added a `referrerPolicy` value,
but it doesn't look like you're checking it anywhere? And you haven't added the
value to any other item in the list?

[Yoav Weiss, 2016/10/23 13:27:09]

my bad. Forgot to add an actual check for the value :/

 };
 
 void PrintTo(const SingleTestCase& test, std::ostream* os) {