Fix failing tests after r151032
Fix failing tests after r151032

r151032 broke inspector/profiler/cpu-profiler-parameterless-profile-end-crash.html
due to missing '[Default=Undefined] optional'.

TBR=abarth

Review URL: https://codereview.chromium.org/15958003

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@151038 bbb929c8-8fbe-4397-9dbb-9b2b20218538

primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs