Part 4.1: Is policy list subsumed under subsuming policy?

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

Index: third_party/WebKit/Source/core/frame/csp/ContentSecurityPolicy.h
diff --git a/third_party/WebKit/Source/core/frame/csp/ContentSecurityPolicy.h b/third_party/WebKit/Source/core/frame/csp/ContentSecurityPolicy.h
index f2f3671052a24586e1052a4e3f4dcf2942c11815..6f32ad9d89516ed5220f206411522b88b90c99e5 100644
--- a/third_party/WebKit/Source/core/frame/csp/ContentSecurityPolicy.h
+++ b/third_party/WebKit/Source/core/frame/csp/ContentSecurityPolicy.h
@@ -366,6 +366,11 @@ class CORE_EXPORT ContentSecurityPolicy
   static bool shouldEnforceEmbeddersPolicy(const ResourceResponse&,
                                            SecurityOrigin*);
 
+  // This method checks if this CSP subsumes given CSP.

[Mike West, 2016/11/28 13:08:02]

Nit: "... if this policy subsumes a given policy"

Should probably also add a comment that it only works if the policy contains
only a single `CSPDirectiveList`.

+  // More information here:
+  // https://w3c.github.io/webappsec-csp/embedded/#subsume-policy
+  bool subsumes(const ContentSecurityPolicy&);
+
   Document* document() const;
 
  private: