we don't do actions that could modify v8 heap so we can report GC events synchronously. Otherwise these GC events would get call stacks of the next event. We will not collect call stacks for gc event at all because it could be triggered even a single small allocation and the call stack will mislead the developer. If someone would like to know what code allocates memory then he needs to use our allocation profiler with allocation stacks.

BUG=361045
R=yurys@chromium.org

Review URL: https://codereview.chromium.org/235043002

git-svn-id: svn://svn.chromium.org/blink/trunk@171460 bbb929c8-8fbe-4397-9dbb-9b2b20218538