Part 2.1: Is policy list subsumed under subsuming policy?

third_party/WebKit/Source/core/frame/csp/SourceListDirective.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/frame/csp/SourceListDirective.h"
 
 #include "core/frame/csp/CSPSource.h"
 #include "core/frame/csp/ContentSecurityPolicy.h"
 #include "platform/network/ContentSecurityPolicyParsers.h"
 #include "platform/weborigin/KURL.h"
@@ skipping 551 matching lines @@
     const KURL& url,
     ResourceRequest::RedirectStatus redirectStatus) const {
   for (size_t i = 0; i < m_list.size(); ++i) {
     if (m_list[i]->matches(url, redirectStatus))
       return true;
   }
 
   return false;
 }
 
+HeapVector<Member<CSPSource>> SourceListDirective::getIntersectCSPSources(
+    HeapVector<Member<CSPSource>> otherVector) {
+  HeapVector<Member<CSPSource>> normalized;
+  for (const auto& aCspSource : m_list) {
+    Member<CSPSource> matchedCspSource(nullptr);
+    for (const auto& bCspSource : otherVector) {
+      if ((matchedCspSource = bCspSource->intersect(aCspSource)))
+        break;
+    }
+    if (matchedCspSource)
+      normalized.append(matchedCspSource);
+  }
+  return normalized;
+}
+
 DEFINE_TRACE(SourceListDirective) {
   visitor->trace(m_policy);
   visitor->trace(m_list);
   CSPDirective::trace(visitor);
 }
 
 }  // namespace blink