MAGETWO-96941: TinyMCE editor JSOON attribute improvement

- Reverted JSON value changes
- Updated JSON utility method

Author: Hwashiang Yu

lib/web/tiny_mce/classes/util/JSON.js

@@ -92,7 +92,7 @@
 		 */
 		parse: function(s) {
 			try {
-				return eval('(' + s + ')');
+				return JSON.parse(s);
 			} catch (ex) {
 				// Ignore
 			}

lib/web/tiny_mce/plugins/media/editor_plugin_src.js

@@ -372,15 +372,9 @@
 			};
 
 			data = node.attr('data-mce-json');
-			if (!data || !data.isJSON())
+			if (!data)
 				return;
 
-			try {
-				data.evalJSON(true);
-			} catch {
-				return;
-			}
-
 			data = JSON.parse(data);
 			typeItem = this.getType(node.attr('class'));