Added command line debugger to D8 shell....

src/debug-delay.js

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1311 matching lines @@
   var break_point = %ToNumber(request.arguments.breakpoint);
 
   // Check for legal arguments.
   if (!break_point) {
     response.failed('Missing argument "breakpoint"');
     return;
   }
 
   // Clear break point.
   Debug.clearBreakPoint(break_point);
+
+  // Add the cleared break point number to the response.
+  response.body = { breakpoint: break_point }
 }
 
 
 DebugCommandProcessor.prototype.backtraceRequest_ = function(request, response) {
   // Get the number of frames.
   var total_frames = this.exec_state_.frameCount();
 
   // Create simple response if there are no frames.
   if (total_frames == 0) {
     response.body = {
@@ skipping 39 matching lines @@
   }
 };
 
 
 DebugCommandProcessor.prototype.backtracec = function(cmd, args) {
   return this.exec_state_.cframesValue();
 };
 
 
 DebugCommandProcessor.prototype.frameRequest_ = function(request, response) {
+  // No frames no source.
+  if (this.exec_state_.frameCount() == 0) {
+    return response.failed('No frames');
+  }
+
   // With no arguments just keep the selected frame.
   if (request.arguments && request.arguments.number >= 0) {
     this.exec_state_.setSelectedFrame(request.arguments.number);
   }
   response.body = this.exec_state_.frame();
 };
 
 
 DebugCommandProcessor.prototype.evaluateRequest_ = function(request, response) {
   if (!request.arguments) {
@@ skipping 45 matching lines @@
   } else {
     // Evaluate in the selected frame.
     response.body = this.exec_state_.frame().evaluate(
         expression, Boolean(disable_break));
     return;
   }
 };
 
 
 DebugCommandProcessor.prototype.sourceRequest_ = function(request, response) {
+  // No frames no source.
+  if (this.exec_state_.frameCount() == 0) {
+    return response.failed('No source');
+  }
+
   var from_line;
   var to_line;
   var frame = this.exec_state_.frame();
   if (request.arguments) {
     // Pull out arguments.
     from_line = request.arguments.fromLine;
     to_line = request.arguments.toLine;
 
     if (!IS_UNDEFINED(request.arguments.frame)) {
       var frame_number = %ToNumber(request.arguments.frame);
@@ skipping 196 matching lines @@
       json += NumberToJSON_(elem);
     } else if (IS_STRING(elem)) {
       json += StringToJSON_(elem);
     } else {
       json += elem;
     }
   }
   json += ']';
   return json;
 }