Without the boundary prototypes we have to keep track of all shadowing properties
throughout the complete prototype chain. This contradicts the finding that most
objects have a rather large number of non-enumerable properties on the prototype
chain.

BUG=v8:705, v8:4905, v8:4706

Review-Url: https://codereview.chromium.org/2038043002
Cr-Commit-Position: refs/heads/master@{#36776}