[serializer] small fixes for blink snapshot.

src/snapshot/startup-serializer.h

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_SNAPSHOT_STARTUP_SERIALIZER_H_
 #define V8_SNAPSHOT_STARTUP_SERIALIZER_H_
 
 #include <bitset>
 #include "include/v8.h"
 #include "src/snapshot/serializer.h"
@@ skipping 12 matching lines @@
   // 1) Immortal immovable roots
   // 2) Remaining strong references.
   // 3) Partial snapshot cache.
   // 4) Weak references (e.g. the string table).
   void SerializeStrongReferences();
   void SerializeWeakReferencesAndDeferred();
 
   int PartialSnapshotCacheIndex(HeapObject* o);
 
  private:
-  class PartialCacheIndexMap : public AddressMapBase {
+  class PartialCacheIndexMap {
    public:
     PartialCacheIndexMap() : map_(), next_index_(0) {}
 
     // Lookup object in the map. Return its index if found, or create
     // a new entry with new_index as value, and return kInvalidIndex.
     bool LookupOrInsert(HeapObject* obj, int* index_out) {
-      base::HashMap::Entry* entry = LookupEntry(&map_, obj, false);
-      if (entry != NULL) {
-        *index_out = GetValue(entry);
+      Maybe<uint32_t> maybe_index = map_.Get(obj);
+      if (maybe_index.IsJust()) {
+        *index_out = maybe_index.FromJust();
         return true;
       }
       *index_out = next_index_;
-      SetValue(LookupEntry(&map_, obj, true), next_index_++);
+      map_.Set(obj, next_index_++);
       return false;
     }
 
    private:
-    base::HashMap map_;
+    DisallowHeapAllocation no_allocation_;
+    HeapObjectToIndexHashMap map_;
     int next_index_;
 
     DISALLOW_COPY_AND_ASSIGN(PartialCacheIndexMap);
   };
 
   // The StartupSerializer has to serialize the root array, which is slightly
   // different.
   void VisitPointers(Object** start, Object** end) override;
   void SerializeObject(HeapObject* o, HowToCode how_to_code,
                        WhereToPoint where_to_point, int skip) override;
@@ skipping 10 matching lines @@
   bool serializing_immortal_immovables_roots_;
   std::bitset<Heap::kStrongRootListLength> root_has_been_serialized_;
   PartialCacheIndexMap partial_cache_index_map_;
   DISALLOW_COPY_AND_ASSIGN(StartupSerializer);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_SNAPSHOT_STARTUP_SERIALIZER_H_