Support getComputedStyle for non-rendered pseudo elements.

Support getComputedStyle for non-rendered pseudo elements.

Computed style for pseudo elements exist and is defined by [1] regardless
of whether the pseudo element, or its ancestor, is rendered or not [2].
We make sure that the computed pseudo element style hangs off of the
RenderStyle of the ancestor, or the computed style in the ancestor's
rare-data if the ancestor is not rendered.

getCachedPseudoStyle, getUncachedPseudoStyle, and pseudoStyleForElement are
all written to not return anything if the pseudo element is not rendered.
That is the reason for calling pseudoStyleForElement in a special mode at
the end of Element::computedStyle to force creating and adding the pseudo
style to the cache.

This CL does not try to support computed style for pseudo elements which
are not in the document.

[1] http://dev.w3.org/csswg/cssom/#dom-window-getcomputedstyle
[2] http://dev.w3.org/csswg/cssom/#::after-pseudo-element

R=esprehn@chromium.org
BUG=414088
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=182203

[rune, 2014-09-17 18:51:10]

PTAL

[esprehn, 2014-09-17 19:04:42]

https://codereview.chromium.org/572043002/diff/1/Source/core/css/resolver/Sty...
File Source/core/css/resolver/StyleResolver.cpp (right):

https://codereview.chromium.org/572043002/diff/1/Source/core/css/resolver/Sty...
Source/core/css/resolver/StyleResolver.cpp:831: if (pseudoStyleRequest.type ==
PseudoStyleRequest::ForRenderer)
This doesn't make sense, pseudoStyleForElementInternal only returns false if
there's no matched properties. If there's no matched properties then you're just
returning the default UA style here. I don't think you're returning the correct
style...

[rune, 2014-09-17 20:00:33]

https://codereview.chromium.org/572043002/diff/1/Source/core/css/resolver/Sty...
File Source/core/css/resolver/StyleResolver.cpp (right):

https://codereview.chromium.org/572043002/diff/1/Source/core/css/resolver/Sty...
Source/core/css/resolver/StyleResolver.cpp:831: if (pseudoStyleRequest.type ==
PseudoStyleRequest::ForRenderer)
On 2014/09/17 at 19:04:42, esprehn wrote:
> This doesn't make sense, pseudoStyleForElementInternal only returns false if
there's no matched properties. If there's no matched properties then you're just
returning the default UA style here. I don't think you're returning the correct
style...

http://www.w3.org/TR/CSS2/generate.html#before-after-content:

"The :before and :after pseudo-elements inherit any inheritable properties from
the element in the document tree to which they are attached."
"In a :before or :after pseudo-element declaration, non-inherited properties
take their initial values."

That is exactly what happens in:

https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

[esprehn, 2014-09-17 21:06:53]

lgtm, okay. Are you sure it's okay to add this cached style and not set the
hasPseudoStyle bits?

[rune, 2014-09-17 22:20:01]

On 2014/09/17 at 21:06:53, esprehn wrote:
> lgtm, okay. Are you sure it's okay to add this cached style and not set the
hasPseudoStyle bits?

Yes, pretty sure after going through the code once more.

[rune, 2014-09-17 22:20:27]

The CQ bit was checked by rune@opera.com

[commit-bot: I haz the power, 2014-09-17 22:20:35]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/572043002/1

[commit-bot: I haz the power, 2014-09-18 00:02:20]

Committed patchset #1 (id:1) as 182203