Combine leaks with same stacktrace

Combine similar leaks (those with identical stack traces) into a single
leak report, and sort the resulting leaks by total leak size across all
similar leaks and their references.

Bug: 27208635
Change-Id: Ia2bf2ccf3fcbc110d1c7ba60e3b77348d1c63d8d
(cherry picked from commit 7a22e81c20e9a28b9cf7b99e0f46659a2b2a9de7)
7 files changed