RFC: use some in-memory state in SimpleCache to quickly cache-miss some CantConditionalize cases

net/http/http_cache.cc

Index: net/http/http_cache.cc
diff --git a/net/http/http_cache.cc b/net/http/http_cache.cc
index eaaffe48c1bf538768e39d46bd5505b71f7e0614..8e55ef64c3de27ea873aa46832ac0d2c1ddbe8f3 100644
--- a/net/http/http_cache.cc
+++ b/net/http/http_cache.cc
@@ -739,7 +739,9 @@ void HttpCache::DeletePendingOp(PendingOp* pending_op) {
   delete pending_op;
 }
 
-int HttpCache::OpenEntry(const std::string& key, ActiveEntry** entry,
+int HttpCache::OpenEntry(const std::string& key,
+                         ActiveEntry** entry,
+                         disk_cache::Backend::OracleCallback oracle_callback,
                          Transaction* trans) {
   ActiveEntry* active_entry = FindActiveEntry(key);
   if (active_entry) {
@@ -747,6 +749,7 @@ int HttpCache::OpenEntry(const std::string& key, ActiveEntry** entry,
     return OK;
   }
 
+  // ### store the oracle callback in this case?
   std::unique_ptr<WorkItem> item =
       base::MakeUnique<WorkItem>(WI_OPEN_ENTRY, trans, entry);
   PendingOp* pending_op = GetPendingOp(key);
@@ -761,8 +764,13 @@ int HttpCache::OpenEntry(const std::string& key, ActiveEntry** entry,
   pending_op->callback = base::Bind(&HttpCache::OnPendingOpComplete,
                                     GetWeakPtr(), pending_op);
 
-  int rv = disk_cache_->OpenEntry(key, &(pending_op->disk_entry),
-                                  pending_op->callback);
+  int rv;
+  if (oracle_callback.is_null())
+    rv = disk_cache_->OpenEntry(key, &(pending_op->disk_entry),
+                                pending_op->callback);
+  else
+    rv = disk_cache_->OpenEntryWithOracleByte(
+        key, &(pending_op->disk_entry), oracle_callback, pending_op->callback);
   if (rv != ERR_IO_PENDING) {
     pending_op->writer->ClearTransaction();
     pending_op->callback.Run(rv);