Check if verdict entry is a dictionary before call FindKey

A CHECK in base::Value::FindKey(..) is hit in a small number of crashes
during shutdown. A check should be in place to make sure the base::Value
instance is in fact a dictionary before calling FindKey(..)

Bug: 890399
Change-Id: I0b24395afc192dbab03f241d94b25309923758d6
Reviewed-on: https://chromium-review.googlesource.com/1252623Reviewed-by: Daniel Rubery <drubery@chromium.org>
Commit-Queue: Jialiu Lin <jialiul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595204}

components/safe_browsing/password_protection/password_protection_service.cc

@@ -676,7 +676,7 @@ bool PasswordProtectionService::ParseVerdictEntry(
     int* out_verdict_received_time,
     LoginReputationClientResponse* out_verdict) {
   std::string serialized_verdict_proto;
-  if (!verdict_entry || !out_verdict)
+  if (!verdict_entry || !verdict_entry->is_dict() || !out_verdict)
     return false;
   base::Value* cache_creation_time_value =
       verdict_entry->FindKey(kCacheCreationTime);