Add generic.total_physical_bytes property to MallocExtension

Add generic.total_physical_bytes property to MallocExtension

The actual physical memory usage of tcmalloc cannot be obtained by
GetNumericProperty. This accounts for the current_allocated_bytes,
fragmentation and malloc metadata, and excludes the unmapped memory
regions. This helps the user to understand how much memory is actually
being used for the allocations that were made.

This change is done only in chromium tree since the
metadata_unmapped_bytes is added only in the chromium's tcmalloc in CL:
www.crrev.com/10499004.

This is to be used by malloc dump provider for tracing.

BUG=546491
Committed: https://crrev.com/0752ec9c6adf641985db1a3a224bf9b8e32e4ac8
Cr-Commit-Position: refs/heads/master@{#357155}

[ssid, 2015-10-27 11:48:51]

ssid@chromium.org changed reviewers:
+ wfh@chromium.org

[ssid, 2015-10-27 11:48:52]

+wfh This changes the tcmalloc files to return the bytes used by metadata, which
currently can be obtained only by MallocExtension::GetStats, but that gives in
human readable format. So, to get the correct value thie new api is needed.
PTAL, Thanks.

[Primiano Tucci (use gerrit), 2015-10-27 17:05:41]

primiano@chromium.org changed reviewers:
+ primiano@chromium.org

[Primiano Tucci (use gerrit), 2015-10-27 17:05:41]

LGTM for base/trace_event.

Note: I think you need to add one line to the "Modifications:" of
README.chromium for tcmalloc

[ssid, 2015-10-30 14:02:31]

Added readme.

wfh@ PTAL, Thanks.

[Will Harris, 2015-10-30 16:33:45]

lgtm. Sorry for delay.

[ssid, 2015-10-30 16:48:55]

The CQ bit was checked by ssid@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-10-30 16:49:16]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1410353005/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1410353005/20001

[commit-bot: I haz the power, 2015-10-30 18:26:07]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-10-30 18:26:07]

Dry run: This issue passed the CQ dry run.

[ssid, 2015-10-30 18:27:56]

The CQ bit was checked by ssid@chromium.org

[ssid, 2015-10-30 18:27:56]

The patchset sent to the CQ was uploaded after l-g-t-m from
primiano@chromium.org
Link to the patchset: https://codereview.chromium.org/1410353005/#ps20001
(title: "Add in readme.")

[commit-bot: I haz the power, 2015-10-30 18:30:24]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1410353005/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1410353005/20001

[commit-bot: I haz the power, 2015-10-30 18:47:48]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-10-30 18:49:08]

Patchset 2 (id:??) landed as
https://crrev.com/0752ec9c6adf641985db1a3a224bf9b8e32e4ac8
Cr-Commit-Position: refs/heads/master@{#357155}