port 44e98103 (r28644)

original commit message:

    When we enter a method that needs access to the [[HomeObject]]
    we allocate a local variable `.home_object` and assign it the
    value from the [[HomeObject]] private symbol. Something along
    the lines of:

      method() {
        var .home_object = %ThisFunction()[home_object_symbol];
        ...
      }

BUG=

Review URL: https://codereview.chromium.org/1158543004

Cr-Commit-Position: refs/heads/master@{#28717}