[debugger] fix stepping over await calls for ignition generators.

src/debug/debug.h

 // Copyright 2012 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.
 
 #ifndef V8_DEBUG_DEBUG_H_
 #define V8_DEBUG_DEBUG_H_
 
 #include "src/allocation.h"
 #include "src/arguments.h"
 #include "src/assembler.h"
@@ skipping 20 matching lines @@
 class DebugScope;
 
 
 // Step actions. NOTE: These values are in macros.py as well.
 enum StepAction : int8_t {
   StepNone = -1,  // Stepping not prepared.
   StepOut = 0,    // Step out of the current function.
   StepNext = 1,   // Step to the next statement in the current function.
   StepIn = 2,     // Step into new functions invoked or the next statement
                   // in the current function.
-  StepFrame = 3   // Step into a new frame or return to previous frame.
+  StepFrame = 3,  // Step into a new frame or return to previous frame.
+
+  LastStepAction = StepFrame
 };
 
-
 // Type of exception break. NOTE: These values are in macros.py as well.
 enum ExceptionBreakType {
   BreakException = 0,
   BreakUncaughtException = 1
 };
 
 
 // Type of exception break.
 enum BreakLocatorType { ALL_BREAK_LOCATIONS, CALLS_AND_RETURNS };
 
@@ skipping 756 matching lines @@
                                   Handle<Code> code);
   static bool DebugBreakSlotIsPatched(Address pc);
   static void ClearDebugBreakSlot(Isolate* isolate, Address pc);
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_DEBUG_DEBUG_H_