LiveEdit: implement frame dropping

src/debug.h

Index: src/debug.h
diff --git a/src/debug.h b/src/debug.h
index 546512b11306ace0f9c576e514c619f71eb5c960..a0e8b818e7a6cf1e88ab356eab28ba6065cd8c21 100644
--- a/src/debug.h
+++ b/src/debug.h
@@ -377,10 +377,18 @@ class Debug {
   static void GenerateConstructCallDebugBreak(MacroAssembler* masm);
   static void GenerateReturnDebugBreak(MacroAssembler* masm);
   static void GenerateStubNoRegistersDebugBreak(MacroAssembler* masm);
+  static void GeneratePlainReturnLiveEdit(MacroAssembler* masm);
+  static void GenerateFrameDropperLiveEdit(MacroAssembler* masm);
 
   // Called from stub-cache.cc.
   static void GenerateCallICDebugBreak(MacroAssembler* masm);
 
+  static void FramesHaveBeenDropped(StackFrame::Id new_break_frame_id);
+
+  static void SetUpFrameDropperFrame(StackFrame* bottom_js_frame,
+                                     Handle<Code> code);
+  static const int kFrameDropperFrameSize;
+
  private:
   static bool CompileDebuggerScript(int index);
   static void ClearOneShot();
@@ -446,6 +454,9 @@ class Debug {
     // Storage location for jump when exiting debug break calls.
     Address after_break_target_;
 
+    // Indicates that LiveEdit has patched the stack.
+    bool frames_are_dropped_;
+
     // Top debugger entry.
     EnterDebugger* debugger_entry_;