Handle insertion order for simple constructors

Handle insertion order for simple constructors

When functions only have simple assignments of the form this.x = ... the object is created in generated code without actually calling the constructor. In this case the initial map for the function already contains the properties assigned in the constructor. The field descriptors in this initial map now has an enumeration index assigned to make property enumeration order the insertion order. The insertion order here is the order of the this.x assignments in the code.

BUG=http://crbug.com/3867
TEST=test/mjsunit/regress/regress-crbug-3867.js

Review URL: http://codereview.chromium.org/566016

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3768 ce2b1a6d-e550-0410-aec6-3dcde31c8c00