Issue #2542 - Part 2: Base implementation of Sec-Fetch-* header code.

Currently following Mozilla putting stuff in /dom for additional porting,
but it's actually the wrong location since it belongs in /netwerk with
the other code that deals with http headers.

netwerk/protocol/http/nsHttpChannel.cpp

@@ -99,6 +99,7 @@
 #include "CacheControlParser.h"
 #include "nsMixedContentBlocker.h"
 #include "CacheStorageService.h"
+#include "mozilla/dom/SecFetch.h"
 
 namespace mozilla { namespace net {
 
@@ -380,6 +381,8 @@ nsHttpChannel::Connect()
                               NS_LITERAL_CSTRING("1"), false);
         NS_ENSURE_SUCCESS(rv, rv);
     }
+    
+    mozilla::dom::SecFetch::AddSecFetchHeader(this);
 
     bool isHttps = false;
     rv = mURI->SchemeIs("https", &isHttps);