This replaces _requestHeapSnapshot and _getObjectByAddresses, which relied on the invalid assumption that objects don't move and the heap hasn't mutated since the initial snapshot.
Updates Observatory to the new format. Adds treemap visualization of the dominator tree. Adds the ability to save and load heap snapshots to files. Removes analysis grouping references by source and target class. Removes ability to navigate from a pixel in the fragmentation view to inspector. Removes ability to query the top retaining instance from an ordinary class browser.
Change-Id: Ia7781c05d43bf3ec149f8b4ecab803b37c3ee981
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/112181
Commit-Queue: Ryan Macnak <rmacnak@google.com>
Reviewed-by: Ben Konyi <bkonyi@google.com>
Ryan Macnak