Added support to backtrace from botton of stack to debugger protocol

src/d8.js

 // Copyright 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 480 matching lines @@
   }
 
   return request.toJSONProtocol();
 };
 
 
 // Create a JSON request for the backtrace command.
 DebugRequest.prototype.backtraceCommandToJSONRequest_ = function(args) {
   // Build a backtrace request from the text command.
   var request = this.createRequest('backtrace');
+  
+  // Default is to show top 10 frames.
+  request.arguments = {};
+  request.arguments.fromFrame = 0;
+  request.arguments.toFrame = 10;
+
   args = args.split(/\s*[ ]+\s*/g);
-  if (args.length == 2) {
-    request.arguments = {};
+  if (args.length == 1 && args[0].length > 0) {
+    var frameCount = parseInt(args[0]);
+    if (frameCount > 0) {
+      // Show top frames.
+      request.arguments.fromFrame = 0;
+      request.arguments.toFrame = frameCount;
+    } else {
+      // Show bottom frames.
+      request.arguments.fromFrame = 0;
+      request.arguments.toFrame = -frameCount;
+      request.arguments.bottom = true;
+    }
+  } else if (args.length == 2) {
     var fromFrame = parseInt(args[0]);
     var toFrame = parseInt(args[1]);
     if (isNaN(fromFrame) || fromFrame < 0) {
       throw new Error('Invalid start frame argument "' + args[0] + '".');
     }
     if (isNaN(toFrame) || toFrame < 0) {
       throw new Error('Invalid end frame argument "' + args[1] + '".');
     }
     if (fromFrame > toFrame) {
       throw new Error('Invalid arguments start frame cannot be larger ' +
                       'than end frame.');
     }
+    // Show frame range.
     request.arguments.fromFrame = fromFrame;
     request.arguments.toFrame = toFrame + 1;
+  } else if (args.length > 2) {
+    throw new Error('Invalid backtrace arguments.');
   }
+
   return request.toJSONProtocol();
 };
 
 
 // Create a JSON request for the frame command.
 DebugRequest.prototype.frameCommandToJSONRequest_ = function(args) {
   // Build a frame request from the text command.
   var request = this.createRequest('frame');
   args = args.split(/\s*[ ]+\s*/g);
   if (args.length > 0 && args[0].length > 0) {
@@ skipping 219 matching lines @@
   // Help os quite simple.
   if (args && args.length > 0) {
     print('warning: arguments to \'help\' are ignored');
   }
 
   print('break location [condition]');
   print('  break on named function: location is a function name');
   print('  break on function: location is #<id>#');
   print('  break on script position: location is name:line[:column]');
   print('clear <breakpoint #>');
-  print('backtrace [from frame #] [to frame #]]');
+  print('backtrace [n] | [-n] | [from to]');
   print('frame <frame #>');
   print('step [in | next | out| min [step count]]');
   print('print <expression>');
   print('source [from line [num lines]]');
   print('scripts');
   print('continue');
   print('trace compile');
   print('help');
 }
 
@@ skipping 689 matching lines @@
       json += NumberToJSON_(elem);
     } else if (typeof(elem) === 'string')  {
       json += StringToJSON_(elem);
     } else {
       json += elem;
     }
   }
   json += ']';
   return json;
 }