Part 5.2: Is policy list subsumed under subsuming policy?

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

Index: third_party/WebKit/Source/core/frame/csp/CSPDirectiveList.cpp
diff --git a/third_party/WebKit/Source/core/frame/csp/CSPDirectiveList.cpp b/third_party/WebKit/Source/core/frame/csp/CSPDirectiveList.cpp
index f202d21f93fa784410b74e0e3d971ba9f764278b..fae3651f2dfb5427bedc8d5ab4c4ea2cbfc95490 100644
--- a/third_party/WebKit/Source/core/frame/csp/CSPDirectiveList.cpp
+++ b/third_party/WebKit/Source/core/frame/csp/CSPDirectiveList.cpp
@@ -1264,7 +1264,16 @@ bool CSPDirectiveList::subsumes(const CSPDirectiveListVector& other) {
       return false;
   }
 
-  return true;
+  if (!m_pluginTypes.get())
+    return true;
+
+  HeapVector<Member<MediaListDirective>> pluginTypesOther;
+  for (const auto& policy : other) {
+    if (policy->m_pluginTypes.get())
+      pluginTypesOther.append(policy->m_pluginTypes);
+  }
+
+  return m_pluginTypes->subsumes(pluginTypesOther);
 }
 
 DEFINE_TRACE(CSPDirectiveList) {