Extending v8::GetHeapStatistics to return total available size.

Extending v8::GetHeapStatistics to return total available size.

For dumping memory statistics about v8 heap, we need the total
available size of the heap. This CL adds extra field in HeapStatistics
to return the available size.

BUG=476013
LOG=Y

Committed: https://crrev.com/0a1352a716e9af5d861dcede0d7c6580f018a10b
Cr-Commit-Position: refs/heads/master@{#28100}

[ssid, 2015-04-27 12:45:54]

ssid@chromium.org changed reviewers:
+ jochen@chromium.org, rmcilroy@chromium.org

[ssid, 2015-04-27 13:07:59]

3 line patch, PTAL.

[jochen (gone - plz use gerrit), 2015-04-27 19:50:23]

lgtm

[rmcilroy, 2015-04-28 09:02:51]

On 2015/04/27 19:50:23, jochen wrote:
> lgtm

lgtm.

[ssid, 2015-04-28 10:21:29]

The CQ bit was checked by ssid@chromium.org

[commit-bot: I haz the power, 2015-04-28 10:21:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1104123002/1

[commit-bot: I haz the power, 2015-04-28 10:24:15]

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

[commit-bot: I haz the power, 2015-04-28 10:24:15]

Try jobs failed on following builders:
  v8_presubmit on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_presubmit/builds/2307)

[ssid, 2015-04-28 10:56:05]

The CQ bit was checked by ssid@chromium.org

[commit-bot: I haz the power, 2015-04-28 10:56:15]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1104123002/1

[commit-bot: I haz the power, 2015-04-28 10:57:45]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-28 10:57:57]

Patchset 1 (id:??) landed as
https://crrev.com/0a1352a716e9af5d861dcede0d7c6580f018a10b
Cr-Commit-Position: refs/heads/master@{#28100}