Record details, such as cumulative duration, number of steps, and longest steps
in IncrementalMarkingDetails which get populated at a single callsite
(AddScopeSample). Remove member fields that thus become obsolete (unfortunately
not all of them).

Additional remove some dead code and refactor printing. Printing in a single
statement allows for using logcat on Android.

This should also address the regression in chromium:640524.

BUG=chromium:639818,chromium:640524
R=jochen@chromium.org

Review-Url: https://codereview.chromium.org/2269093002
Cr-Commit-Position: refs/heads/master@{#38912}