[ast] Simplify NewBoilerplateDescription.

The property backing store size depends on the number of
index keys. Pass index keys to the factory function instead
calculating the size outside.

R=verwaest@chromium.org

BUG=v8:5625

Review-Url: https://codereview.chromium.org/2651533002
Cr-Commit-Position: refs/heads/master@{#42637}

src/ast/ast.cc

@@ -604,9 +604,9 @@ void ObjectLiteral::BuildConstantProperties(Isolate* isolate) {
   }
 
   Handle<BoilerplateDescription> constant_properties =
-      isolate->factory()->NewBoilerplateDescription(
-          boilerplate_properties_, properties()->length() - index_keys,
-          has_seen_proto);
+      isolate->factory()->NewBoilerplateDescription(boilerplate_properties_,
+                                                    properties()->length(),
+                                                    index_keys, has_seen_proto);
 
   int position = 0;
   for (int i = 0; i < properties()->length(); i++) {

src/factory.cc

@@ -186,10 +186,13 @@ Handle<FixedArray> Factory::NewUninitializedFixedArray(int size) {
 }
 
 Handle<BoilerplateDescription> Factory::NewBoilerplateDescription(
-    int boilerplate, int all_properties, bool has_seen_proto) {
-  DCHECK_GE(all_properties, 0);
+    int boilerplate, int all_properties, int index_keys, bool has_seen_proto) {
+  DCHECK_GE(boilerplate, 0);
+  DCHECK_GE(all_properties, index_keys);
+  DCHECK_GE(index_keys, 0);
 
-  int backing_store_size = all_properties - (has_seen_proto ? 1 : 0);
+  int backing_store_size =
+      all_properties - index_keys - (has_seen_proto ? 1 : 0);
   DCHECK_GE(backing_store_size, 0);
   bool has_different_size_backing_store = boilerplate != backing_store_size;
 
@@ -205,7 +208,7 @@ Handle<BoilerplateDescription> Factory::NewBoilerplateDescription(
       Handle<BoilerplateDescription>::cast(NewFixedArray(size, TENURED));
 
   if (has_different_size_backing_store) {
-    DCHECK((boilerplate != all_properties) || has_seen_proto);
+    DCHECK((boilerplate != (all_properties - index_keys)) || has_seen_proto);
     description->set_backing_store_size(isolate(), backing_store_size);
   }
   return description;

src/factory.h

@@ -52,6 +52,7 @@ class V8_EXPORT_PRIVATE Factory final {
   // calculates the number of properties we need to store in the backing store.
   Handle<BoilerplateDescription> NewBoilerplateDescription(int boilerplate,
                                                            int all_properties,
+                                                           int index_keys,
                                                            bool has_seen_proto);
 
   // Allocate a new uninitialized fixed double array.