Use a pointer type for values in DocumentOrderedMap

Use a pointer type for values in DocumentOrderedMap

Use a pointer type for values in DocumentOrderedMap (OwnPtr<MapEntry>) instead
of a struct type (MapEntry). This should hopefully fix the performance
regression on Bindings/get-element-by-id micro benchmark caused by r164029 on
some platforms.

While this CL seems to have no performance impact on Linux Desktop, I see a 14%
improvement on Bindings/get-element-by-id micro benchmark on Android (tested on
Galaxy Note 3 device). This may be due to HashTable optimizations when the
empty value for ValueType is zero, or to better caching.

R=esprehn, abarth
BUG=330778
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=164440

[abarth-chromium, 2014-01-03 03:01:29]

LGTM

It's usually better to store pointers in HashMaps because the HashMap's table is
bloated by the size of its values.

[commit-bot: I haz the power, 2014-01-03 03:01:43]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/123333003/1

[commit-bot: I haz the power, 2014-01-03 03:07:43]

Change committed as 164440