Introduce AsyncDocumentSubresourceFilter.

components/subresource_filter/core/common/indexed_ruleset.cc

Index: components/subresource_filter/core/common/indexed_ruleset.cc
diff --git a/components/subresource_filter/core/common/indexed_ruleset.cc b/components/subresource_filter/core/common/indexed_ruleset.cc
index 75ac71767ddad07faa5e441b0157fb824304d306..b5455cc368ffbf4ce6bfb291c09ccc36dd4e1e1a 100644
--- a/components/subresource_filter/core/common/indexed_ruleset.cc
+++ b/components/subresource_filter/core/common/indexed_ruleset.cc
@@ -470,10 +470,10 @@ bool IsMatch(const flat::UrlPatternIndex* index,
 
 }  // namespace
 
+// static
 bool IndexedRulesetMatcher::Verify(const uint8_t* buffer, size_t size) {
-  const auto* indexed_ruleset = flat::GetIndexedRuleset(buffer);
   flatbuffers::Verifier verifier(buffer, size);
-  return indexed_ruleset->Verify(verifier);
+  return flat::VerifyIndexedRulesetBuffer(verifier);
 }
 
 IndexedRulesetMatcher::IndexedRulesetMatcher(const uint8_t* buffer, size_t size)