Part 2.2: Is policy list subsumed under subsuming policy?

third_party/WebKit/Source/core/frame/csp/CSPSource.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/CSPSource.h"
 
 #include "core/frame/UseCounter.h"
 #include "core/frame/csp/ContentSecurityPolicy.h"
 #include "platform/weborigin/KURL.h"
 #include "platform/weborigin/KnownPorts.h"
@@ skipping 144 matching lines @@
   WildcardDisposition portWildcard =
       (m_portWildcard == HasWildcard) ? other->m_portWildcard : m_portWildcard;
   return new CSPSource(m_policy, scheme, host, port, path, hostWildcard,
                        portWildcard);
 }
 
 bool CSPSource::isSchemeOnly() const {
   return m_host.isEmpty();
 }
 
+bool CSPSource::firstSubsumesSecond(HeapVector<Member<CSPSource>> listA,
+                                    HeapVector<Member<CSPSource>> listB) {
+  // Empty vector of CSPSources has an effect of 'none'.
+  if (!listA.size() || !listB.size())
+    return !listB.size();
+
+  // Walk through all the items in |listB|, ensuring that each is subsumed by at
+  // least one item in |listA|. If any item in |listB| is not subsumed, return
+  // false.
+  for (const auto& sourceB : listB) {
+    bool foundMatch = false;
+    for (const auto& sourceA : listA) {
+      if ((foundMatch = sourceA->subsumes(sourceB)))
+        break;
+    }
+    if (!foundMatch)
+      return false;
+  }
+  return true;
+}
+
 DEFINE_TRACE(CSPSource) {
   visitor->trace(m_policy);
 }
 
 }  // namespace blink