commit 1b79bbcdc1c9fee58cec0da6b19afd75d0bb47c9
author Richard Uhler <ruhler@google.com> Fri Oct 20 10:41:50 2017 +0100
committer Richard Uhler <ruhler@google.com> Thu Oct 26 16:18:45 2017 +0100
tree eece222b38346dd07a78c1783f92654140b91637
parent 9041c606de11412a036bac2d2068d6f151a0fab7

Fix bugs with strong versus weak reference paths.

This fixes a few issues with strong versus weak reference paths:
* It was possible to have a path from gc root with a root in the
  middle of the path.
* It was possible to have a path from gc root with a cycle, which
  would cause ahat to go into an infinite loop.
* It was still possible to have a path from gc root through weak
  references when there existed other paths from gc root only through
  strong references.

Bug: 64592321

Test: m ahat-test, with new tests added.
Change-Id: I2d3cc8c5a398aad24d70c3a428bdc3a470ddb3aa