Adds SB V4 response handler to Protocol Manager.

components/safe_browsing_db/util.h

Index: components/safe_browsing_db/util.h
diff --git a/components/safe_browsing_db/util.h b/components/safe_browsing_db/util.h
index daa202ef8c9a072cdab5bf19eb6fe1e113afc95a..d2e46ee68fd14ada187b6db82257b3ea61fa8944 100644
--- a/components/safe_browsing_db/util.h
+++ b/components/safe_browsing_db/util.h
@@ -65,6 +65,9 @@ struct SBFullHashResult {
   // TODO(shess): Refactor to allow ListType here.
   int list_id;
   std::string metadata;
+  // Used only for V4 results. The cache lifetime for this result. The response
+  // must not be cached for more than this duration to avoid false positives.
+  base::TimeDelta cache_duration;

[Nathan Parker, 2016/01/11 23:50:32]

How does this relate to the SBCachedFullHashResult::expire_after? Is
expire_after not used for v4 responses?

[kcarattini, 2016/01/12 00:43:34]

SBCachedFullHashResult is used by the database, and it looks like it takes the
cache_lifetime passed to the callback and sets that value for all hashes in the
cache that were part of the same request. In V4, there can be a different
cache_duration per hash (as opposed to per request), so we need a way to capture
that in the results that are passed to the callback. If we end up using the
SBCachedFullHashResult in the database manager (and I suspect we will), then
yes, this cache_duration will be used to the the expire_after field.

 };
 
 // Caches individual response from GETHASH request.