The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6081ba4689b78d110f637cad0bb29d25fd09e771

commit 6081ba4689b78d110f637cad0bb29d25fd09e771
Author: Etienne Bergeron <etienneb@chromium.org>
Date: Wed Sep 20 20:26:48 2017

Group variadic allocations with same stackframe

The variadic allocations were kept separately which may bring allocation
sites for string to be pruned. This patch is merging them. An allocation
is uniquify based on it's stackframe and it's context-id, and no longer
on the size.

Basically, we are moving |size| from "key" to the "values" of the
map used to group allocations.

R=erikchen@chromium.org, brettw@chromium.org

Bug:  762056 
Change-Id: Ic8b674c96be603b335234799cbcf6dcf53033869
Reviewed-on: https://chromium-review.googlesource.com/664226
Commit-Queue: Etienne Bergeron <etienneb@chromium.org>
Reviewed-by: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#503236}
[modify] https://crrev.com/6081ba4689b78d110f637cad0bb29d25fd09e771/chrome/browser/profiling_host/memlog_browsertest.cc
[modify] https://crrev.com/6081ba4689b78d110f637cad0bb29d25fd09e771/chrome/profiling/json_exporter.cc
[modify] https://crrev.com/6081ba4689b78d110f637cad0bb29d25fd09e771/chrome/profiling/json_exporter_unittest.cc