List scope chain levels and their variables to the selected stack frame. (#2557)

It supports to list the scope chain of the current execution context and see
which variables are available.

JerryScript-DCO-1.0-Signed-off-by: Robert Sipka rsipka.uszeged@partner.samsung.com

tests/debugger/do_variables.js

@@ -0,0 +1,60 @@
+// Copyright JS Foundation and other contributors, http://js.foundation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+var c = 4;
+var z = 5;
+
+function addX(x) {
+  return function(n) {
+    var b = 2;
+    return n + x;
+  }
+}
+
+addThree = addX(3);
+d = addThree(c+z);
+
+function f() {
+  try {
+    throw "error";
+  }
+  catch (err) {
+    var c = 10;
+  }
+
+  var m = null;
+
+  var user = {
+    name: "John",
+    age: 30
+  };
+
+  var x = true;
+  var b = 10;
+
+  (function() {
+    var a = [1,2,3]
+    a.y = "abc";
+    with (a) {
+      var h = [4,5,6]
+      with (h) {
+        h.d = "dfg"
+      }
+      a.d = x;
+    }
+  })();
+}
+
+f();
+