Revert "Resolve references to "this" the same way as normal variables"

Revert "Resolve references to "this" the same way as normal variables"

... and the following two
"PPC: Resolve references to "this" the same way as normal variables"
"Remove Scope::scope_uses_this_ flag"

R=hablich@chromium.org
BUG=chromium:487289
LOG=N

Review URL: https://codereview.chromium.org/1134003003

Cr-Commit-Position: refs/heads/master@{#28395}