Add a UMA to measure the amount of memory consumed in PartitionAlloc

Add a UMA to measure the amount of memory consumed in PartitionAlloc

This UMA will be used in https://codereview.chromium.org/1053793004/.

BUG=471650
Committed: https://crrev.com/aa6d6c6545d6322c2b82d5a132e7aa59910abfbe
Cr-Commit-Position: refs/heads/master@{#323690}

[haraken, 2015-04-02 12:32:01]

haraken@chromium.org changed reviewers:
+ isherman@chromium.org, mpearson@google.com, oilpan-reviews@chromium.org

[haraken, 2015-04-02 12:32:01]

PTAL

[Ilya Sherman, 2015-04-02 17:10:04]

https://codereview.chromium.org/1051203002/diff/1/tools/metrics/histograms/hi...
File tools/metrics/histograms/histograms.xml (right):

https://codereview.chromium.org/1051203002/diff/1/tools/metrics/histograms/hi...
tools/metrics/histograms/histograms.xml:24856: +  <summary>The committed memory
size in PartitionAlloc.</summary>
Please document when this is recorded.

[haraken, 2015-04-02 23:35:33]

Thanks for review!

>
https://codereview.chromium.org/1051203002/diff/1/tools/metrics/histograms/hi...
> File tools/metrics/histograms/histograms.xml (right):
> 
>
https://codereview.chromium.org/1051203002/diff/1/tools/metrics/histograms/hi...
> tools/metrics/histograms/histograms.xml:24856: +  <summary>The committed
memory
> size in PartitionAlloc.</summary>
> Please document when this is recorded.

Done.

[Ilya Sherman, 2015-04-03 01:01:29]

LGTM

[haraken, 2015-04-03 01:04:00]

The CQ bit was checked by haraken@chromium.org

[commit-bot: I haz the power, 2015-04-03 04:43:36]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1051203002/20001

[commit-bot: I haz the power, 2015-04-03 08:04:05]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-04-03 20:35:24]

Patchset 2 (id:??) landed as
https://crrev.com/aa6d6c6545d6322c2b82d5a132e7aa59910abfbe
Cr-Commit-Position: refs/heads/master@{#323690}