RenderLayerScrollableArea shouldn't call updateLayerCompositingState

RenderLayerScrollableArea shouldn't call updateLayerCompositingState

Conceptually, there's no reason for RenderLayerScrollableArea to call
updateLayerCompositingState and no tests fail when the call is removed.

BUG=343756, 336251
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=175937

[chrishtr, 2014-06-11 01:20:42]

On 2014/06/11 at 01:15:29, abarth wrote:
> 

Could you at least do some code archaeology to see who added it?

[esprehn, 2014-06-11 01:21:37]

lgtm,

What does updateLayerCompositingState actually do though?

[abarth-chromium, 2014-06-11 01:30:36]

On 2014/06/11 at 01:21:37, esprehn wrote:
> What does updateLayerCompositingState actually do though?

Nowadays, it updates the non-style determined compositing reasons reasons
(useless) and sometimes sets CompositingUpdateRebuildTree.

The caller in RenderLayer::styleChanged passes UseChickenEggHacks, which
actually makes it do exciting things like create or destroy
CompositedLayerMappings.

[abarth-chromium, 2014-06-11 01:31:31]

On 2014/06/11 at 01:20:42, chrishtr wrote:
> Could you at least do some code archaeology to see who added it?

Oh, I'm sure this used to do something useful when updateLayerCompositingState
actually did a lot of work and when we didn't compute the upgrade to
CompositingUpdateRebuildTree properly in the compositing update.

[abarth-chromium, 2014-06-11 01:31:53]

On 2014/06/11 at 01:31:31, abarth wrote:
> On 2014/06/11 at 01:20:42, chrishtr wrote:
> > Could you at least do some code archaeology to see who added it?
> 
> Oh, I'm sure this used to do something useful when updateLayerCompositingState
actually did a lot of work and when we didn't compute the upgrade to
CompositingUpdateRebuildTree properly in the compositing update.

But for you, I'll look when this was added.  :)

[abarth-chromium, 2014-06-11 01:40:25]

It was added in
https://chromium.googlesource.com/chromium/blink/+/db004747d992e66c1cfb0fec30...
as part of adding accelerated overflow scrolling.

[abarth-chromium, 2014-06-11 01:40:30]

The CQ bit was checked by abarth@chromium.org

[commit-bot: I haz the power, 2014-06-11 01:41:28]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/abarth@chromium.org/321283003/1

[commit-bot: I haz the power, 2014-06-11 02:34:51]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  linux_blink_dbg on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_dbg/builds/1...)
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/11523)

[commit-bot: I haz the power, 2014-06-11 03:36:40]

Change committed as 175937