Part 2.2: Is policy list subsumed under subsuming policy?

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

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/frame/csp/CSPSource.h"
 
 #include "core/frame/UseCounter.h"
 #include "core/frame/csp/ContentSecurityPolicy.h"
 #include "platform/weborigin/KURL.h"
 #include "platform/weborigin/KnownPorts.h"
@@ skipping 144 matching lines @@
   WildcardDisposition portWildcard =
       (m_portWildcard == HasWildcard) ? other->m_portWildcard : m_portWildcard;
   return new CSPSource(m_policy, scheme, host, port, path, hostWildcard,
                        portWildcard);
 }
 
 bool CSPSource::isSchemeOnly() const {
   return m_host.isEmpty();
 }
 
+bool CSPSource::firstSubsumesSecond(HeapVector<Member<CSPSource>> a,
+                                    HeapVector<Member<CSPSource>> b) {

[Mike West, 2016/11/10 15:04:54]

Nit: `listA`, `listB`?

+  // Empty vector of CSPSources has an effect of 'none'.
+  if (a.size() == 0 || b.size() == 0)
+    return b.size() == 0;

[Mike West, 2016/11/10 15:04:54]

Nit: For all of these, you can write `a.size() == 0` as `!a.size()`. We usually
do that rather than comparing to 0.

+
+  for (const auto& bCspSrc : b) {

[Mike West, 2016/11/10 15:04:54]

Please add a comment here: something like "Walk through all the items in
|listB|, ensuring that each is subsumed by at least one item in |listA|. If any
item in |listB| is not subsumed, return false."

+    bool foundMatch = false;
+    for (const auto& aCspSrc : a) {
+      if ((foundMatch = aCspSrc->subsumes(bCspSrc)))

[Mike West, 2016/11/10 15:04:54]

Nit: `sourceA`, `sourceB`?

+        break;
+    }
+    if (!foundMatch)
+      return false;
+  }
+  return true;
+}
+
 DEFINE_TRACE(CSPSource) {
   visitor->trace(m_policy);
 }
 
 }  // namespace blink