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

src/runtime/runtime-debug.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/debug/debug-evaluate.h"
 #include "src/debug/debug-frames.h"
 #include "src/debug/debug-scopes.h"
@@ skipping 1680 matching lines @@
 // built-in function such as Array.forEach to enable stepping into the callback,
 // if we are indeed stepping and the callback is subject to debugging.
 RUNTIME_FUNCTION(Runtime_DebugPrepareStepInIfStepping) {
   HandleScope scope(isolate);
   DCHECK_EQ(1, args.length());
   CONVERT_ARG_HANDLE_CHECKED(JSFunction, fun, 0);
   isolate->debug()->PrepareStepIn(fun);
   return isolate->heap()->undefined_value();
 }
 
+// Set one shot breakpoints for the suspended generator object.
+RUNTIME_FUNCTION(Runtime_DebugPrepareStepInSuspendedGenerator) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(0, args.length());
+  isolate->debug()->PrepareStepInSuspendedGenerator();
+  return isolate->heap()->undefined_value();
+}
 
 RUNTIME_FUNCTION(Runtime_DebugPushPromise) {
   DCHECK(args.length() == 2);
   HandleScope scope(isolate);
   CONVERT_ARG_HANDLE_CHECKED(JSObject, promise, 0);
   CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 1);
   isolate->PushPromise(promise, function);
   // If we are in step-in mode, flood the handler.
   isolate->debug()->EnableStepIn();
   return isolate->heap()->undefined_value();
@@ skipping 22 matching lines @@
   return Smi::FromInt(isolate->debug()->is_active());
 }
 
 
 RUNTIME_FUNCTION(Runtime_DebugBreakInOptimizedCode) {
   UNIMPLEMENTED();
   return NULL;
 }
 }  // namespace internal
 }  // namespace v8