Dramatically speed up detailed heap snapshot generation.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 01073ca7b08bd272520e1b1009d266a671411e7e..be57e1ea83afd699e27ae6e0add93acf1860a409 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -861,6 +861,11 @@ MaybeObject* Object::GetProperty(String* key, PropertyAttributes* attributes) {
   (*reinterpret_cast<byte*>(FIELD_ADDR(p, offset)) = value)
 
 
+Address HeapObject::GetFieldAddress(int offset) {
+  return reinterpret_cast<Address>(RawField(this, offset));
+}
+
+
 Object** HeapObject::RawField(HeapObject* obj, int byte_offset) {
   return &READ_FIELD(obj, byte_offset);
 }
@@ -1313,6 +1318,13 @@ int JSObject::GetInternalFieldCount() {
 }
 
 
+Address JSObject::GetInternalFieldOffset(int index) {
+  ASSERT(index < GetInternalFieldCount() && index >= 0);
+  return reinterpret_cast<Address>(
+      &READ_FIELD(this, GetHeaderSize() + (kPointerSize * index)));
+}
+
+
 Object* JSObject::GetInternalField(int index) {
   ASSERT(index < GetInternalFieldCount() && index >= 0);
   // Internal objects do follow immediately after the header, whereas in-object
@@ -1336,6 +1348,18 @@ void JSObject::SetInternalField(int index, Object* value) {
 // Access fast-case object properties at index. The use of these routines
 // is needed to correctly distinguish between properties stored in-object and
 // properties stored in the properties array.
+Address JSObject::GetFastPropertyAddress(int index) {
+  // Adjust for the number of properties stored in the object.
+  index -= map()->inobject_properties();
+  if (index < 0) {
+    int offset = map()->instance_size() + (index * kPointerSize);
+    return reinterpret_cast<Address>(&READ_FIELD(this, offset));
+  } else {
+    return NULL;
+  }
+}
+
+
 Object* JSObject::FastPropertyAt(int index) {
   // Adjust for the number of properties stored in the object.
   index -= map()->inobject_properties();