[bindings] Compact ConstantConfiguration by using |union|

[bindings] Compact ConstantConfiguration by using |union|

This patch uses |union| to store the constant values to reduce space required.

This patch saves about ~4 Kbytes of in |.data.rel.ro.local| with component build on linux platform.
Also the size of V8DOMConfiguration::ConstantConfiguration is down to 24 bytes from
40 bytes on 64bit linux build.

BUG=469961
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=201193

[vivekg, 2015-08-25 14:04:48]

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

[vivekg, 2015-08-25 14:04:52]

The CQ bit was unchecked by vivekg@chromium.org

[vivekg, 2015-08-25 14:06:24]

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

[commit-bot: I haz the power, 2015-08-25 14:06:32]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1310443005/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1310443005/1

[vivekg, 2015-08-25 14:07:27]

The CQ bit was unchecked by vivekg@chromium.org

[vivekg, 2015-08-25 17:45:52]

vivekg@chromium.org changed reviewers:
+ haraken@chromium.org

[vivekg, 2015-08-25 17:47:50]

PTAL and let me know your thoughts on this. Thanks!

[haraken, 2015-08-25 23:32:43]

LGTM

[haraken, 2015-08-25 23:34:20]

We haven't yet studied how much binary size is consumed by these static data
structures in the binding layer (there are a lot of static data structures). It
would be worth getting a number and reducing.

[vivekg, 2015-08-26 00:24:11]

On 2015/08/25 23:34:20, haraken wrote:
> We haven't yet studied how much binary size is consumed by these static data
> structures in the binding layer (there are a lot of static data structures).
It
> would be worth getting a number and reducing.

Yes I have started looking into it. Thanks.

[vivekg, 2015-08-26 00:24:18]

The CQ bit was checked by vivekg@chromium.org

[commit-bot: I haz the power, 2015-08-26 00:24:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1310443005/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1310443005/1

[commit-bot: I haz the power, 2015-08-26 03:22:37]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=201193