DescriptorArray::IsProperty-related cleanup.

More minor changes related to property predicates:

 * Slightly simplify logic when handling hidden properties.

 * Make IsProperty usage more consistent in RemoveTransitions.

Review URL: https://chromiumcodereview.appspot.com/9352012

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10617 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/objects.cc

@@ -3773,12 +3773,14 @@ MaybeObject* JSObject::GetHiddenPropertiesDictionary(bool create_if_absent) {
     // code zero) it will always occupy the first entry if present.
     DescriptorArray* descriptors = this->map()->instance_descriptors();
     if ((descriptors->number_of_descriptors() > 0) &&
-        (descriptors->GetKey(0) == GetHeap()->hidden_symbol()) &&
-        descriptors->IsProperty(0)) {
-      ASSERT(descriptors->GetType(0) == FIELD);
+        (descriptors->GetKey(0) == GetHeap()->hidden_symbol())) {
+      if (descriptors->GetType(0) == FIELD) {
         Object* hidden_store =
             this->FastPropertyAt(descriptors->GetFieldIndex(0));
         return StringDictionary::cast(hidden_store);
+      } else {
+        ASSERT(descriptors->GetType(0) == MAP_TRANSITION);
+      }
     }
   } else {
     PropertyAttributes attributes;
@@ -3819,11 +3821,13 @@ MaybeObject* JSObject::SetHiddenPropertiesDictionary(
     // code zero) it will always occupy the first entry if present.
     DescriptorArray* descriptors = this->map()->instance_descriptors();
     if ((descriptors->number_of_descriptors() > 0) &&
-        (descriptors->GetKey(0) == GetHeap()->hidden_symbol()) &&
-        descriptors->IsProperty(0)) {
-      ASSERT(descriptors->GetType(0) == FIELD);
+        (descriptors->GetKey(0) == GetHeap()->hidden_symbol())) {
+      if (descriptors->GetType(0) == FIELD) {
         this->FastPropertyAtPut(descriptors->GetFieldIndex(0), dictionary);
         return this;
+      } else {
+        ASSERT(descriptors->GetType(0) == MAP_TRANSITION);
+      }
     }
   }
   MaybeObject* store_result =
@@ -5832,14 +5836,14 @@ MaybeObject* DescriptorArray::RemoveTransitions() {
   // not be allocated.
 
   // Compute the size of the map transition entries to be removed.
-  int num_removed = 0;
+  int new_number_of_descriptors = 0;
   for (int i = 0; i < number_of_descriptors(); i++) {
-    if (!IsProperty(i)) num_removed++;
+    if (IsProperty(i)) new_number_of_descriptors++;
   }
 
   // Allocate the new descriptor array.
   DescriptorArray* new_descriptors;
-  { MaybeObject* maybe_result = Allocate(number_of_descriptors() - num_removed);
+  { MaybeObject* maybe_result = Allocate(new_number_of_descriptors);
     if (!maybe_result->To<DescriptorArray>(&new_descriptors)) {
       return maybe_result;
     }