Create an abstraction for the string type flags so that they can be cached....

src/api.cc

 // Copyright 2007-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2017 matching lines @@
 }
 
 
 int String::WriteAscii(char* buffer, int start, int length) {
   if (IsDeadCheck("v8::String::WriteAscii()")) return 0;
   LOG_API("String::WriteAscii");
   ASSERT(start >= 0 && length >= -1);
   i::Handle<i::String> str = Utils::OpenHandle(this);
   // Flatten the string for efficiency.  This applies whether we are
   // using StringInputBuffer or Get(i) to access the characters.
-  str->TryFlatten();
+  str->TryFlatten(i::StringShape(*str));
   int end = length;
   if ( (length == -1) || (length > str->length() - start) )
     end = str->length() - start;
   if (end < 0) return 0;
   write_input_buffer.Reset(start, *str);
   int i;
   for (i = 0; i < end; i++) {
     char c = static_cast<char>(write_input_buffer.GetNext());
     if (c == '\0') c = ' ';
     buffer[i] = c;
   }
   if (length == -1 || i < length)
     buffer[i] = '\0';
   return i;
 }
 
 
 int String::Write(uint16_t* buffer, int start, int length) {
   if (IsDeadCheck("v8::String::Write()")) return 0;
   LOG_API("String::Write");
   ASSERT(start >= 0 && length >= -1);
   i::Handle<i::String> str = Utils::OpenHandle(this);
   // Flatten the string for efficiency.  This applies whether we are
   // using StringInputBuffer or Get(i) to access the characters.
-  str->TryFlatten();
+  str->TryFlatten(i::StringShape(*str));
   int end = length;
   if ( (length == -1) || (length > str->length() - start) )
     end = str->length() - start;
   if (end < 0) return 0;
   write_input_buffer.Reset(start, *str);
   int i;
   for (i = 0; i < end; i++)
     buffer[i] = write_input_buffer.GetNext();
   if (length == -1 || i < length)
     buffer[i] = '\0';
   return i;
 }
 
 
 bool v8::String::IsExternal() {
   EnsureInitialized("v8::String::IsExternal()");
   i::Handle<i::String> str = Utils::OpenHandle(this);
-  return str->IsExternalTwoByteString();
+  i::StringShape shape(*str);
+  return shape.IsExternalTwoByte();
 }
 
 
 bool v8::String::IsExternalAscii() {
   EnsureInitialized("v8::String::IsExternalAscii()");
   i::Handle<i::String> str = Utils::OpenHandle(this);
-  return str->IsExternalAsciiString();
+  i::StringShape shape(*str);
+  return shape.IsExternalAscii();
 }
 
 
 v8::String::ExternalStringResource* v8::String::GetExternalStringResource() {
   EnsureInitialized("v8::String::GetExternalStringResource()");
   i::Handle<i::String> str = Utils::OpenHandle(this);
   ASSERT(str->IsExternalTwoByteString());
   void* resource = i::Handle<i::ExternalTwoByteString>::cast(str)->resource();
   return reinterpret_cast<ExternalStringResource*>(resource);
 }
@@ skipping 867 matching lines @@
       reinterpret_cast<HandleScopeImplementer*>(storage);
   List<void**>* blocks_of_archived_thread = thread_local->Blocks();
   ImplementationUtilities::HandleScopeData* handle_data_of_archived_thread =
       &thread_local->handle_scope_data_;
   Iterate(v, blocks_of_archived_thread, handle_data_of_archived_thread);
 
   return storage + ArchiveSpacePerThread();
 }
 
 } }  // namespace v8::internal