Add ExternalStringResourceBase::IsCompressible

src/factory.cc

Index: src/factory.cc
diff --git a/src/factory.cc b/src/factory.cc
index 3a933dd32f6dd362e2a7afa2d0cb5d55c471d3ab..bb051280cc0118585cb2521c8a25b80a7e8505a5 100644
--- a/src/factory.cc
+++ b/src/factory.cc
@@ -670,7 +670,12 @@ MaybeHandle<String> Factory::NewExternalStringFromOneByte(
     THROW_NEW_ERROR(isolate(), NewInvalidStringLengthError(), String);
   }
 
-  Handle<Map> map = external_one_byte_string_map();
+  Handle<Map> map;
+  if (resource->isCompressible()) {
+    map = short_external_one_byte_string_map();

[Yang, 2015/12/17 11:41:53]

Please add a TODO to rename this to "uncached_external_one_byte_string_map()"
and similar for other short external string maps.
Or do the renaming in this CL.

[hajimehoshi, 2016/01/05 08:07:44]

Done.

+  } else {
+    map = external_one_byte_string_map();
+  }
   Handle<ExternalOneByteString> external_string =
       New<ExternalOneByteString>(map, NEW_SPACE);
   external_string->set_length(static_cast<int>(length));
@@ -693,8 +698,14 @@ MaybeHandle<String> Factory::NewExternalStringFromTwoByte(
   static const size_t kOneByteCheckLengthLimit = 32;
   bool is_one_byte = length <= kOneByteCheckLengthLimit &&
       String::IsOneByte(resource->data(), static_cast<int>(length));
-  Handle<Map> map = is_one_byte ?
-      external_string_with_one_byte_data_map() : external_string_map();
+  Handle<Map> map;
+  if (resource->isCompressible()) {
+    map = is_one_byte ? short_external_string_with_one_byte_data_map()
+                      : short_external_string_map();
+  } else {
+    map = is_one_byte ? external_string_with_one_byte_data_map()
+                      : external_string_map();
+  }
   Handle<ExternalTwoByteString> external_string =
       New<ExternalTwoByteString>(map, NEW_SPACE);
   external_string->set_length(static_cast<int>(length));