Check the validity of cache_ weak ptr in DoFinishHeaders

net/http/http_cache_transaction.cc

Index: net/http/http_cache_transaction.cc
diff --git a/net/http/http_cache_transaction.cc b/net/http/http_cache_transaction.cc
index dd17ae57b38abec3c4c61e5f4943eb2fff3d8ad3..51bf85f1f519846379487643e06e2bd07b306a34 100644
--- a/net/http/http_cache_transaction.cc
+++ b/net/http/http_cache_transaction.cc
@@ -1833,7 +1833,7 @@ int HttpCache::Transaction::DoHeadersPhaseCannotProceed() {
 }
 
 int HttpCache::Transaction::DoFinishHeaders(int result) {
-  if (!entry_ || result != OK) {
+  if (!cache_.get() || !entry_ || result != OK) {
     TransitionToState(STATE_NONE);
     return result;
   }