LiveEdit: implement stack manipulations for x64

src/debug.h

Index: src/debug.h
diff --git a/src/debug.h b/src/debug.h
index b6aba5aad1bf65ebffd6ec29bce0c7ea7254b640..98d1919423af4471ee9658507fb955f889c62958 100644
--- a/src/debug.h
+++ b/src/debug.h
@@ -400,6 +400,11 @@ class Debug {
   static void GenerateStubNoRegistersDebugBreak(MacroAssembler* masm);
   static void GenerateSlotDebugBreak(MacroAssembler* masm);
   static void GeneratePlainReturnLiveEdit(MacroAssembler* masm);
+
+  // FrameDropper is a code replacement for a JavaScript frame with possibly
+  // several frames above.
+  // There is no calling conventions here, because it never actually gets
+  // called, it only gets returned to.
   static void GenerateFrameDropperLiveEdit(MacroAssembler* masm);
 
   // Called from stub-cache.cc.
@@ -431,13 +436,14 @@ class Debug {
   // the value that is called 'restarter_frame_function_pointer'. The value
   // at this address (possibly updated by GC) may be used later when preparing
   // 'step in' operation.
-  // The implementation is architecture-specific.
-  // TODO(LiveEdit): consider reviewing it as architecture-independent.
   static Object** SetUpFrameDropperFrame(StackFrame* bottom_js_frame,
                                          Handle<Code> code);
 
   static const int kFrameDropperFrameSize;
 
+  // Architecture-specific constant.
+  static const bool kFrameDropperSupported;
+
  private:
   static bool CompileDebuggerScript(int index);
   static void ClearOneShot();