Added support to backtrace from botton of stack to debugger protocol

test/mjsunit/debug-backtrace.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 106 matching lines @@
     var frames = backtrace.frames;
     assertEquals(2, frames.length);
     for (var i = 0; i < frames.length; i++) {
       assertEquals('frame', frames[i].type);
     }
     assertEquals(1, frames[0].index);
     assertEquals("g", response.lookup(frames[0].func.ref).name);
     assertEquals(2, frames[1].index);
     assertEquals("", response.lookup(frames[1].func.ref).name);
 
+    // Get backtrace with bottom two frames.
+    json = '{"seq":0,"type":"request","command":"backtrace","arguments":{"fromFrame":0,"toFrame":2, "bottom":true}}'
+    response = new ParsedResponse(dcp.processDebugJSONRequest(json));
+    backtrace = response.body();
+    assertEquals(1, backtrace.fromFrame);
+    assertEquals(3, backtrace.toFrame);
+    assertEquals(3, backtrace.totalFrames);
+    var frames = backtrace.frames;
+    assertEquals(2, frames.length);
+    for (var i = 0; i < frames.length; i++) {
+      assertEquals('frame', frames[i].type);
+    }
+    assertEquals(1, frames[0].index);
+    assertEquals("g", response.lookup(frames[0].func.ref).name);
+    assertEquals(2, frames[1].index);
+    assertEquals("", response.lookup(frames[1].func.ref).name);
+
     // Get the individual frames.
     json = '{"seq":0,"type":"request","command":"frame"}'
     response = new ParsedResponse(dcp.processDebugJSONRequest(json));
     frame = response.body();
     assertEquals(0, frame.index);
     assertEquals("f", response.lookup(frame.func.ref).name);
     assertTrue(frame.constructCall);
     assertEquals(31, frame.line);
     assertEquals(3, frame.column);
     assertEquals(2, frame.arguments.length);
@@ skipping 81 matching lines @@
 Debug.setListener(listener);
 
 // Set a break point and call to invoke the debug event listener.
 Debug.setBreakPoint(f, 0, 0);
 g();
 
 // Make sure that the debug event listener vas invoked.
 assertFalse(exception, "exception in listener");
 assertTrue(listenerCalled);