Now we don't need to call collectSample on each V8StackTraceImpl::capture during collecting profile.

CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_precise_blink_rel
BUG=none
R=alph@chromium.org,dgozman@chromium.org

Review-Url: https://codereview.chromium.org/2510823002
Cr-Commit-Position: refs/heads/master@{#41051}