Split TemplateHashMapImpl::Lookup into two methods

src/scanner.cc

Index: src/scanner.cc
diff --git a/src/scanner.cc b/src/scanner.cc
index 8059289b7705d982d77767251f26961bdea8f60a..1dae1e42cd4c8f726cf95916205066782dc35fcd 100644
--- a/src/scanner.cc
+++ b/src/scanner.cc
@@ -1441,7 +1441,7 @@ int DuplicateFinder::AddSymbol(Vector<const uint8_t> key,
                                int value) {
   uint32_t hash = Hash(key, is_one_byte);
   byte* encoding = BackupKey(key, is_one_byte);
-  HashMap::Entry* entry = map_.Lookup(encoding, hash, true);
+  HashMap::Entry* entry = map_.LookupOrInsert(encoding, hash);
   int old_value = static_cast<int>(reinterpret_cast<intptr_t>(entry->value));
   entry->value =
     reinterpret_cast<void*>(static_cast<intptr_t>(value | old_value));