Add metrics for tracking time between "script loaded" and "script compiled".
Add metrics for tracking time between "script loaded" and "script compiled".

The histograms will be used for monitoring the effects of script
streaming (parsing and loading simultaneously).

R=jochen@chromium.org
BUG=

Review URL: https://codereview.chromium.org/531693002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@181225 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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