Shrinking CSSParserToken for lower CSS parsing memory usage.

Shrinking CSSParserToken for lower CSS parsing memory usage.

For 64-bit this shrinks CSSParserToken from 32 to 24 bytes. For 32-bit
this shrinks CSSParserToken from 24 to 20 bytes.

On typical sites (gmail, arstechnica) there are 300 KB stylesheets
which makes us preallocate room for 100,000 CSSParserTokens.
Allocation savings will then be 800 KB on 64-bit and 400 KB on
32-bit.

It does not cause any noticable performance change in any direction
on a workstation. Memory starved devices *might* benefit.

R=timloh@chromium.org
BUG=490185
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=196134

[Daniel Bratell, 2015-05-28 13:03:39]

Patchset #1 (id:1) has been deleted

[Daniel Bratell, 2015-05-28 13:14:45]

timloh, this saves 1+ MB of memory usage during loading of gmail. I really tried
to see if there was a performance change but I don't think there is one. I got
some results that said this was 0.2% faster at parsing gmail CSS but I think
that was noise since repeating measurements said that there was no significant
change.

[Timothy Loh, 2015-05-29 03:27:46]

lgtm

dstockwell: We have perf tests now that will notice changes to parsing
performance, right?

https://codereview.chromium.org/1161963002/diff/20001/Source/core/css/parser/...
File Source/core/css/parser/CSSParserToken.h (right):

https://codereview.chromium.org/1161963002/diff/20001/Source/core/css/parser/...
Source/core/css/parser/CSSParserToken.h:131: const LChar* m_valueDataChar8;
We don't use the explicitly typed versions here.

[dstockwell, 2015-05-29 06:25:33]

On 2015/05/29 at 03:27:46, timloh wrote:
> lgtm
> 
> dstockwell: We have perf tests now that will notice changes to parsing
performance, right?

I'll watch the blink_style graphs. So we'll see, they haven't moved much yet.

[Daniel Bratell, 2015-05-29 11:20:54]

The CQ bit was checked by bratell@opera.com

[Daniel Bratell, 2015-05-29 11:20:54]

The patchset sent to the CQ was uploaded after l-g-t-m from timloh@chromium.org
Link to the patchset: https://codereview.chromium.org/1161963002/#ps40001
(title: "Removed unused union members.")

[commit-bot: I haz the power, 2015-05-29 11:21:09]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1161963002/40001

[commit-bot: I haz the power, 2015-05-29 11:24:44]

Committed patchset #2 (id:40001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=196134