Fix undeclared variable in d8 debugger.

BUG=v8:2033
TEST='list' command works in d8 debugger.
Review URL: https://chromiumcodereview.appspot.com/9861017

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11155 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/d8.js

@@ -2174,7 +2174,7 @@ function DebugResponseDetails(response) {
           }
 
           var current_line = from_line + num;
-          spacer = maxdigits - (1 + Math.floor(log10(current_line)));
+          var spacer = maxdigits - (1 + Math.floor(log10(current_line)));
           if (current_line == Debug.State.currentSourceLine + 1) {
             for (var i = 0; i < maxdigits; i++) {
               result += '>';