Fix incorrect animation for some values of background-position.

Fix incorrect animation for some values of background-position.

There is a bug which causes incorrect animation for background-position
values with right/bottom edge origin. This is because we interpolate
the offset value itself, but do not take into account that the offset
value represents different positions based on the edge origin of the
offset.

Example: If we want to animate from "left 10px" to "right 20px", we
interpolate 10px to 20px, but "forget" the edge affinitiy of the second
value, and end up with a value offset from the left.

Fixed by emitting calculated lengths for bottom/right edge origins during
animation, such that "right N" or "bottom N" becomes "calc(100% - N)".

BUG=341440
TEST=automated

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=166997

[pdr., 2014-02-10 20:50:04]

Steve, Alan, ping? This has been waiting for a little while.

[dstockwell, 2014-02-10 22:24:22]

On 2014/02/10 20:50:04, pdr wrote:
> Steve, Alan, ping? This has been waiting for a little while.

Removed Steve as he no longer works on Blink. Alan should review this.

[alancutter (OOO until 2018), 2014-02-11 00:23:22]

Thanks for fixing this!
lgtm with nits.

Could the test be moved to
LayoutTests/animation/interpolation/background-position-origin-interpolation.html?

https://codereview.chromium.org/157523002/diff/1/Source/core/animation/css/CS...
File Source/core/animation/css/CSSAnimatableValueFactory.cpp (right):

https://codereview.chromium.org/157523002/diff/1/Source/core/animation/css/CS...
Source/core/animation/css/CSSAnimatableValueFactory.cpp:185:
CSSCalcValue::createExpressionNode(length, 1),
The zoom argument should be style.effectiveZoom().

[dstockwell, 2014-02-11 00:26:13]

On 2014/02/11 00:23:22, alancutter wrote:
> Could the test be moved to
>
LayoutTests/animation/interpolation/background-position-origin-interpolation.html?

... and converted to an interpolation test? Or just supplement
background-position-interpolation.

[alancutter (OOO until 2018), 2014-02-11 01:10:31]

On 2014/02/11 00:26:13, dstockwell wrote:
> On 2014/02/11 00:23:22, alancutter wrote:
> > Could the test be moved to
> >
>
LayoutTests/animation/interpolation/background-position-origin-interpolation.html?
> 
> ... and converted to an interpolation test? Or just supplement
> background-position-interpolation.

I think it's different enough to be in its own test file.
Converting it to an interpolation test would be ideal.

[andersr, 2014-02-11 08:32:32]

Thanks for reviewing.

> interpolation test

Yes, I noticed that this test type existed *after* I submitted the patch. I'll
convert it.

[andersr, 2014-02-11 09:34:07]

PTAL, gentlemen.

[alancutter (OOO until 2018), 2014-02-12 00:21:13]

On 2014/02/11 09:34:07, andersr wrote:
> PTAL, gentlemen.

lgtm.

[andersr, 2014-02-12 08:59:44]

The CQ bit was checked by andersr@opera.com

[andersr, 2014-02-12 08:59:45]

The CQ bit was unchecked by andersr@opera.com

[andersr, 2014-02-12 08:59:48]

The CQ bit was checked by andersr@opera.com

[commit-bot: I haz the power, 2014-02-12 09:00:00]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/andersr@opera.com/157523002/110001

[commit-bot: I haz the power, 2014-02-12 09:16:03]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-02-12 09:16:04]

Retried try job too often on blink_presubmit for step(s) presubmit
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=blink_pres...

[dstockwell, 2014-02-12 09:30:59]

rslgtm

[dstockwell, 2014-02-12 09:31:04]

The CQ bit was checked by dstockwell@chromium.org

[commit-bot: I haz the power, 2014-02-12 09:31:18]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/andersr@opera.com/157523002/110001

[commit-bot: I haz the power, 2014-02-12 10:56:33]

Change committed as 166997