DevTools: Implement a workaround for missing stacks in CPU profiler
DevTools: Implement a workaround for missing stacks in CPU profiler

Sometimes sampler is not able to parse the JS stack and returns
a (program) sample instead. The issue leads to call frames belong
to the same function invocation being split apart.
Here's a workaround for that. When there's a single (program) sample
between two call stacks sharing the same bottom node, it is replaced
with the preceeding sample.

Review URL: https://codereview.chromium.org/245153002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@172388 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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