[serializer] small fixes for blink snapshot.

src/address-map.cc

Index: src/address-map.cc
diff --git a/src/address-map.cc b/src/address-map.cc
index 3122b33693488e5e27c1e36881d89d8fa7fc9b1e..79f8e62d5454f23ceb173e19b01993828a2d90e0 100644
--- a/src/address-map.cc
+++ b/src/address-map.cc
@@ -13,7 +13,7 @@ namespace internal {
 RootIndexMap::RootIndexMap(Isolate* isolate) {
   map_ = isolate->root_index_map();
   if (map_ != NULL) return;
-  map_ = new base::HashMap();
+  map_ = new HeapObjectToIndexHashMap();
   for (uint32_t i = 0; i < Heap::kStrongRootListLength; i++) {
     Heap::RootListIndex root_index = static_cast<Heap::RootListIndex>(i);
     Object* root = isolate->heap()->root(root_index);
@@ -22,12 +22,12 @@ RootIndexMap::RootIndexMap(Isolate* isolate) {
     // not be referenced through the root list in the snapshot.
     if (isolate->heap()->RootCanBeTreatedAsConstant(root_index)) {
       HeapObject* heap_object = HeapObject::cast(root);
-      base::HashMap::Entry* entry = LookupEntry(map_, heap_object, false);
-      if (entry != NULL) {
+      Maybe<uint32_t> maybe_index = map_->Get(heap_object);
+      if (maybe_index.IsJust()) {
         // Some are initialized to a previous value in the root list.
-        DCHECK_LT(GetValue(entry), i);
+        DCHECK_LT(maybe_index.FromJust(), i);
       } else {
-        SetValue(LookupEntry(map_, heap_object, true), i);
+        map_->Set(heap_object, i);
       }
     } else {
       // Immortal immovable root objects are constant and allocated on the first