Part 2.2: Is policy list subsumed under subsuming policy?

third_party/WebKit/Source/core/frame/csp/CSPSource.h

Index: third_party/WebKit/Source/core/frame/csp/CSPSource.h
diff --git a/third_party/WebKit/Source/core/frame/csp/CSPSource.h b/third_party/WebKit/Source/core/frame/csp/CSPSource.h
index 63e9cae422f94b43bb086747f19a0d9d10633831..3753491eb454d578de228c3a73f50f197771bed7 100644
--- a/third_party/WebKit/Source/core/frame/csp/CSPSource.h
+++ b/third_party/WebKit/Source/core/frame/csp/CSPSource.h
@@ -38,6 +38,11 @@ class CORE_EXPORT CSPSource : public GarbageCollectedFinalized<CSPSource> {
   // Retrieve the most restrictive information from the two CSPSources if
   // isSimilar is true for the two. Otherwise, return nullptr.
   CSPSource* intersect(CSPSource*);
+  // Returns true if the first list subsumes the second, as defined by the
+  // algorithm at
+  // https://w3c.github.io/webappsec-csp/embedded/#subsume-source-list
+  static bool firstSubsumesSecond(HeapVector<Member<CSPSource>>,
+                                  HeapVector<Member<CSPSource>>);
 
   DECLARE_TRACE();