[debug] implement intuitive semantics for stepping over await call.

src/assembler.cc

Index: src/assembler.cc
diff --git a/src/assembler.cc b/src/assembler.cc
index 35eac01c7b8effb4bfe06748f4e263aec7be5866..e93d42e8547bd63e25c99b332845615c6f79cb9d 100644
--- a/src/assembler.cc
+++ b/src/assembler.cc
@@ -1792,6 +1792,10 @@ ExternalReference ExternalReference::debug_step_in_enabled_address(
   return ExternalReference(isolate->debug()->step_in_enabled_address());
 }
 
+ExternalReference ExternalReference::debug_suspended_generator_address(
+    Isolate* isolate) {
+  return ExternalReference(isolate->debug()->suspended_generator_address());
+}
 
 ExternalReference ExternalReference::fixed_typed_array_base_data_offset() {
   return ExternalReference(reinterpret_cast<void*>(