0. Record and save a large timeline (I'm using 96M, which was obtained by less than 2 minutes of compose-discard in gmail) 1. Close and open inspector 2. Load timeline recorded at step 0 3. Assure "Live native memory chart" experiment is enabled 4. Open inspector on inspector 5. Take a heap snapshot of the inspector with large timeline loaded 6. Compare snapshot size to JS heap size. I'm getting 132M for the former and 162 for the latter.
Closing as invalid, as this bug pertains to the old inspector UI and/or its tests. Please file a new bug (https://www.webkit.org/new-inspector-bug) if the bug/feature/issue is still relevant to WebKit trunk.