[generators] Implement %GeneratorGetSourcePosition.

src/runtime/runtime-generator.cc

Index: src/runtime/runtime-generator.cc
diff --git a/src/runtime/runtime-generator.cc b/src/runtime/runtime-generator.cc
index 493e5b5a9c7935f2644ab09b730998d4fffe76a7..e4f02602f42d52d11d82ccce1833174839593752 100644
--- a/src/runtime/runtime-generator.cc
+++ b/src/runtime/runtime-generator.cc
@@ -146,13 +146,7 @@ RUNTIME_FUNCTION(Runtime_GeneratorGetSourcePosition) {
   CONVERT_ARG_HANDLE_CHECKED(JSGeneratorObject, generator, 0);
 
   if (!generator->is_suspended()) return isolate->heap()->undefined_value();
-
-  if (generator->function()->shared()->HasBytecodeArray()) UNIMPLEMENTED();
-
-  Handle<Code> code(generator->function()->code(), isolate);
-  int offset = generator->continuation();
-  CHECK(0 <= offset && offset < code->instruction_size());
-  return Smi::FromInt(code->SourcePosition(offset));
+  return Smi::FromInt(generator->source_position());
 }
 
 }  // namespace internal