Remove usage of Locker/Unlocker where possible.

src/d8-readline.cc

Index: src/d8-readline.cc
diff --git a/src/d8-readline.cc b/src/d8-readline.cc
index 225c6f06a222a1cfe8ac01c9c68b9cde9344406d..a11cf4dc80cd58db1424960b6ec17b8da063f6f0 100644
--- a/src/d8-readline.cc
+++ b/src/d8-readline.cc
@@ -82,10 +82,7 @@ bool ReadLineEditor::Close() {
 
 Handle<String> ReadLineEditor::Prompt(const char* prompt) {
   char* result = NULL;
-  {  // Release lock for blocking input.
-    Unlocker unlock(isolate_);
-    result = readline(prompt);
-  }
+  result = readline(prompt);
   if (result == NULL) return Handle<String>();
   AddHistory(result);
   return String::NewFromUtf8(isolate_, result);
@@ -123,7 +120,6 @@ char* ReadLineEditor::CompletionGenerator(const char* text, int state) {
   static unsigned current_index;
   static Persistent<Array> current_completions;
   Isolate* isolate = read_line_editor.isolate_;
-  Locker lock(isolate);
   HandleScope scope(isolate);
   Handle<Array> completions;
   if (state == 0) {