DCHECK that full hash must be 21 bytes or 32 bytes long.

components/safe_browsing_db/v4_store.cc

Index: components/safe_browsing_db/v4_store.cc
diff --git a/components/safe_browsing_db/v4_store.cc b/components/safe_browsing_db/v4_store.cc
index 34eaa27e516cb02164f8ccbb5876b64dbad17108..42133e47348a33fda5a6a82657c16969299e0d8e 100644
--- a/components/safe_browsing_db/v4_store.cc
+++ b/components/safe_browsing_db/v4_store.cc
@@ -764,7 +764,6 @@ HashPrefix V4Store::GetMatchingHashPrefix(const FullHash& full_hash) {
   // It should never be the case that more than one hash prefixes match a given
   // full hash. However, if that happens, this method returns any one of them.
   // It does not guarantee which one of those will be returned.
-  DCHECK_EQ(32u, full_hash.size());
   for (const auto& pair : hash_prefix_map_) {

[Nathan Parker, 2017/01/04 18:58:46]

Why isn't this causing crashes all the time? Do we have tests that would hit
this?

One idea: Since we're only expecting 32 and 21 byte strings here, we could check
for those.  That'd prevent a new Check*() method from incorrectly passing the
wrong string here, I think.

[vakh (use Gerrit instead), 2017/01/10 03:47:56]

Because it is executed only for MatchMalwareIP and that wasn't getting executed
yet.
We have tests for MatchMalwareIP but they were replacing the V4Store with a fake
class so they never this this code. Added one in v4_store_unittest.cc now
Done.

     const PrefixSize& prefix_size = pair.first;
     const HashPrefixes& hash_prefixes = pair.second;