This is a workaround to make the debugger happy about TurboFan frames
when the debugger causes frame inspection. Note that this can happen
because the debugger can be activated while there still are optimized
TurboFan activations on the stack.

R=ishell@chromium.org
BUG=chromium:465298
TEST=mjsunit/regress/regress-crbug-465298
LOG=N

Review URL: https://codereview.chromium.org/1074793003

Cr-Commit-Position: refs/heads/master@{#27717}