debugger: support mirroring Date objects

* fixes #3203

lib/_debugger.js

@@ -541,6 +541,8 @@ Client.prototype.mirrorObject = function(handle, depth, cb) {
 
       if (handle.className == 'Array') {
         mirror = [];
+      } else if (handle.className == 'Date') {
+        mirror = new Date(handle.value);
       } else {
         mirror = {};
       }

test/fixtures/breakpoints.js

@@ -17,3 +17,7 @@ b();
 
 setInterval(function() {
 }, 5000);
+
+
+now = new Date();
+debugger;

test/simple/test-debugger-repl.js

@@ -143,6 +143,19 @@ addTest('c', [
   /\d/, /\d/, /\d/, /\d/, /\d/
 ]);
 
+addTest('c', [
+  /break in .*breakpoints.js:\d+/,
+  /\d/, /\d/, /\d/, /\d/, /\d/
+]);
+
+addTest('repl', [
+  /Press Ctrl \+ C to leave debug repl/
+]);
+
+addTest('now', [
+  /\w* \w* \d* \d* \d*:\d*:\d* GMT[+-]\d* (\w*)/
+]);
+
 function finish() {
   process.exit(0);
 }