Modifies readline() to behave in the same way as it does in TraceMonkey.

src/d8.cc

Index: src/d8.cc
===================================================================
--- src/d8.cc	(revision 2740)
+++ src/d8.cc	(working copy)
@@ -180,15 +180,15 @@
 
 
 Handle<Value> Shell::ReadLine(const Arguments& args) {
-  char line_buf[256];
-  if (fgets(line_buf, sizeof(line_buf), stdin) == NULL) {
-    return ThrowException(String::New("Error reading line"));
+  i::SmartPointer<char> line(i::ReadLine(""));
+  if (*line == NULL) {
+    return Null();
   }
-  int len = strlen(line_buf);
-  if (line_buf[len - 1] == '\n') {
+  size_t len = strlen(*line);
+  if (len > 0 && line[len - 1] == '\n') {
     --len;
   }
-  return String::New(line_buf, len);
+  return String::New(*line, len);
 }