Part 1.1: 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 b049bf6c87966def6e30c4eb3fb72696f106021d..57d6ca730b236a2e7b2614da4036991943a976a0 100644
--- a/third_party/WebKit/Source/core/frame/csp/CSPSource.h
+++ b/third_party/WebKit/Source/core/frame/csp/CSPSource.h
@@ -32,6 +32,10 @@ class CORE_EXPORT CSPSource : public GarbageCollectedFinalized<CSPSource> {
                ResourceRequest::RedirectStatus =
                    ResourceRequest::RedirectStatus::NoRedirect) const;
 
+  // Returns true if this CSPSource subsumes the other, as defined by the
+  // algorithm at https://w3c.github.io/webappsec-csp/embedded/#subsume-policy
+  bool subsumes(CSPSource*);
+
   DECLARE_TRACE();
 
  private: