sync: Remove IDs from OrderedCommitSet

sync: Remove IDs from OrderedCommitSet

Remove the IDs from OrderedCommitSet in order to add a new member,
AddCommitItems().

Removing the IDs from this class would have been a good idea on its own.
There hasn't been any need to track both IDs and metahandles for quite
some time, and storing redundant information always carries the risk
that the two copies will disagree with each other. It is particularly
risky in this case because the entries' IDs will be changed when a
commit response is successful.

The AddCommitItems() function would have needed to have an inconvenient
signature if it had to pass in both the handles and IDs of all the
entries being added to the set.  It's much easier to implement now that
we only need to pass in the entries' metahandles.

The new member function is not used in this commit.  It will be used in
a future commit that allows us to run GetCommitIdsCommand on a single
model type at a time.

BUG=278484
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=221154

[rlarocque, 2013-08-28 22:15:31]

Please review.

I plan to remove OrderedCommitSet eventually, so this will seem a bit pointless
in the end.  However, I think the other patches will be easier to review if we
proceed in this order.

[Nicolas Zea, 2013-09-03 22:45:00]

LGTM, although the commit message makes it sound a bit like you're advocating
removing ID's altogether, which this patch isn't really about, so maybe update
that to be a bit clearer.

[rlarocque, 2013-09-03 22:50:58]

On 2013/09/03 22:45:00, Nicolas Zea wrote:
> LGTM, although the commit message makes it sound a bit like you're advocating
> removing ID's altogether, which this patch isn't really about, so maybe update
> that to be a bit clearer.

Done.  I can see how that second paragraph could be misleading.

[commit-bot: I haz the power, 2013-09-03 22:51:57]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rlarocque@chromium.org/23694004/1

[commit-bot: I haz the power, 2013-09-04 04:51:05]

Change committed as 221154