[V8] Add FunctionMirror.prototype.contextDebugId method

src/runtime/runtime-function.cc

Index: src/runtime/runtime-function.cc
diff --git a/src/runtime/runtime-function.cc b/src/runtime/runtime-function.cc
index 081f092f253d0decee3fbb089be37b28531c1179..db830849f2c5f5d8c19c80c1df09cc0219ebe11a 100644
--- a/src/runtime/runtime-function.cc
+++ b/src/runtime/runtime-function.cc
@@ -96,6 +96,14 @@ RUNTIME_FUNCTION(Runtime_FunctionGetPositionForOffset) {
   return Smi::FromInt(abstract_code->SourcePosition(offset));
 }
 
+RUNTIME_FUNCTION(Runtime_FunctionGetContextDebugId) {
+  SealHandleScope shs(isolate);
+  DCHECK(args.length() == 1);
+
+  CONVERT_ARG_CHECKED(JSFunction, fun, 0);
+  FixedArray* array = fun->native_context()->embedder_data();
+  return array->get(v8::Context::kDebugIdIndex);
+}
 
 RUNTIME_FUNCTION(Runtime_FunctionSetInstanceClassName) {
   SealHandleScope shs(isolate);