Handle initial values in background-repeat introduced by the background shorthand

Handle initial values in background-repeat introduced by the background shorthand

background-repeat serialization did not handle initial keyword values in
background-repeat value lists.
Initial values in value lists are introduced by setting the background
shorthand to multiple background values while omitting background-repeat
properties.
Example: background: url(#1), url(#2), url(#3);
The background-repeat gets stored internally as "initial, initial, initial".

This patch updates StylePropertySerializer::backgroundRepeatPropertyValue()
to handle this case correctly.

BUG=378167
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=175261

[rune, 2014-05-31 22:36:01]

https://codereview.chromium.org/303993003/diff/40001/Source/core/css/StylePro...
File Source/core/css/StylePropertySerializer.cpp (right):

https://codereview.chromium.org/303993003/diff/40001/Source/core/css/StylePro...
Source/core/css/StylePropertySerializer.cpp:707: // FIXME: Ensure initial values
do not appear in CSS_VALUE_LISTS.

Shouldn't this be fixed instead?

This seems to be broken for background-attachment as well.

[alancutter (OOO until 2018), 2014-06-01 03:57:37]

https://codereview.chromium.org/303993003/diff/40001/Source/core/css/StylePro...
File Source/core/css/StylePropertySerializer.cpp (right):

https://codereview.chromium.org/303993003/diff/40001/Source/core/css/StylePro...
Source/core/css/StylePropertySerializer.cpp:707: // FIXME: Ensure initial values
do not appear in CSS_VALUE_LISTS.
On 2014/05/31 22:36:01, rune wrote:
> 
> Shouldn't this be fixed instead?
> 
> This seems to be broken for background-attachment as well.

That was my initial approach but the change was getting too large for the type
of bug I'm fixing.
It also has implications for the way we serialise shorthand properties as we
would no longer know whether an initial value was specified as initial or the
equivalent initial value. Too much yak shave for this particular bug.

[rune, 2014-06-02 06:54:49]

https://codereview.chromium.org/303993003/diff/40001/Source/core/css/StylePro...
File Source/core/css/StylePropertySerializer.cpp (right):

https://codereview.chromium.org/303993003/diff/40001/Source/core/css/StylePro...
Source/core/css/StylePropertySerializer.cpp:707: // FIXME: Ensure initial values
do not appear in CSS_VALUE_LISTS.
On 2014/06/01 03:57:37, alancutter wrote:
> On 2014/05/31 22:36:01, rune wrote:
> > 
> > Shouldn't this be fixed instead?
> > 
> > This seems to be broken for background-attachment as well.
> 
> That was my initial approach but the change was getting too large for the type
> of bug I'm fixing.
> It also has implications for the way we serialise shorthand properties as we
> would no longer know whether an initial value was specified as initial or the
> equivalent initial value. Too much yak shave for this particular bug.

I cannot access the issue for this CL in bugs.chromium.org, btw. So I don't know
the importance for it.

I reckon this it's a larger piece of work to fix this properly. Also,
getLayeredShorthandValue have FIXME and Bug references. This code needs some
proper fixing in general it seems.

I'd really love to see this code reworked.

As a local fix this lgtm, but perhaps there are other owners who have stronger
opinions and more knowledge in this area.

[alancutter (OOO until 2018), 2014-06-02 08:03:39]

On 2014/06/02 06:54:49, rune wrote:
> I reckon this it's a larger piece of work to fix this properly. Also,
> getLayeredShorthandValue have FIXME and Bug references. This code needs some
> proper fixing in general it seems.
> 
> I'd really love to see this code reworked.
> 
> As a local fix this lgtm, but perhaps there are other owners who have stronger
> opinions and more knowledge in this area.

Thanks for understanding. I agree this area needs work including the FIXME I
added here, I would like to fix the initial list bug in my spare cycles.

[alancutter (OOO until 2018), 2014-06-02 08:03:44]

The CQ bit was checked by alancutter@chromium.org

[commit-bot: I haz the power, 2014-06-02 08:04:10]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/alancutter@chromium.org/303993003/40001

[commit-bot: I haz the power, 2014-06-02 09:16:21]

Change committed as 175261