DevTools: Wrong eval in console of a shadowed variable.

Shadowing is introduced by evaluating an original expression in the
Console API scope object using the "with(...)" wrapper.
The scope object should have empty __proto__ so that it should not expose
Object.prototype too early in the scope chain.

BUG=237709
R=yurys, pfeldman

Review URL: https://codereview.chromium.org/136733002

git-svn-id: svn://svn.chromium.org/blink/trunk@164976 bbb929c8-8fbe-4397-9dbb-9b2b20218538