inline property access of object literal (#2209)

- only if property value is side-effect-free
- guard by `unsafe`

fixes #2208

lib/compress.js

@@ -4307,6 +4307,17 @@ merge(Compressor.prototype, {
         return self;
     });
 
+    AST_Lambda.DEFMETHOD("contains_this", function() {
+        var result;
+        var self = this;
+        self.walk(new TreeWalker(function(node) {
+            if (result) return true;
+            if (node instanceof AST_This) return result = true;
+            if (node !== self && node instanceof AST_Scope) return true;
+        }));
+        return result;
+    });
+
     OPT(AST_Dot, function(self, compressor){
         var def = self.resolve_defines(compressor);
         if (def) {
@@ -4321,6 +4332,20 @@ merge(Compressor.prototype, {
                 })
             }).optimize(compressor);
         }
+        if (compressor.option("unsafe") && self.expression instanceof AST_Object) {
+            var values = self.expression.properties;
+            for (var i = values.length; --i >= 0;) {
+                if (values[i].key === prop) {
+                    var value = values[i].value;
+                    if (value instanceof AST_Function ? !value.contains_this() : !value.has_side_effects(compressor)) {
+                        var obj = self.expression.clone();
+                        obj.properties = obj.properties.slice();
+                        obj.properties.splice(i, 1);
+                        return make_sequence(self, [ obj, value ]).optimize(compressor);
+                    }
+                }
+            }
+        }
         if (compressor.option("unsafe_proto")
             && self.expression instanceof AST_Dot
             && self.expression.property == "prototype") {