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())

[sof, 2016/12/13 13:38:54]

There is an implicit pointer conversion in place for Member<>, so you can avoid
the explicit get() here. Or (!hasPluginTypes())

+    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);

[Mike West, 2016/12/13 13:54:47]

This looks like it's checking the union of all the policies in |other|, rather
than the intersection, which doesn't seem correct. That is, given `type/1 type/2
type/3` and `type/1`, `type/1` should subsume, but it doesn't look like it will.
Is that accurate?

Can you add some tests along those lines so we can verify the behavior?

[amalika, 2016/12/13 14:42:08]

As with `SourceListDirective`, `subsumes` method of MediaListDirective makes
sure to call `getIntersect` inside. So this should not be finding a union.
I will add tests below already added in SubsumesPluginTypes

 }
 
 DEFINE_TRACE(CSPDirectiveList) {