[wasm] Implement stepping in wasm code

src/wasm/wasm-objects.h

 // Copyright 2016 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_WASM_OBJECTS_H_
 #define V8_WASM_OBJECTS_H_
 
 #include "src/debug/debug.h"
 #include "src/debug/interface-types.h"
 #include "src/objects-inl.h"
@@ skipping 404 matching lines @@
     kFieldCount
   };
 
   static Handle<WasmDebugInfo> New(Handle<WasmInstanceObject>);
 
   static bool IsDebugInfo(Object*);
   static WasmDebugInfo* cast(Object*);
 
   static void SetBreakpoint(Handle<WasmDebugInfo>, int func_index, int offset);
 
+  void PrepareStep(StepAction);
+
   void RunInterpreter(int func_index, uint8_t* arg_buffer);
 
   // Get the stack of the wasm interpreter as pairs of <function index, byte
   // offset>. The list is ordered bottom-to-top, i.e. caller before callee.
   std::vector<std::pair<uint32_t, int>> GetInterpretedStack(
       Address frame_pointer);
 
   std::unique_ptr<wasm::InterpretedFrame> GetInterpretedFrame(
       Address frame_pointer, int idx);
 
@@ skipping 55 matching lines @@
   };
 };
 
 #undef DECLARE_ACCESSORS
 #undef DECLARE_OPTIONAL_ACCESSORS
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_OBJECTS_H_