Move NinePieceImage painting to a separate class

Move NinePieceImage painting to a separate class

While doing as little changes as possible, move NinePieceImage
painting code out of BoxPainter into a separate class. This is in
preparation for the possibility of splitting the function into smaller
parts. The function currently has roughly 36 local variables and is
quite hard to understand and change.

BUG=492485
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=196301

[davve, 2015-05-29 14:16:16]

davve@opera.com changed reviewers:
+ pdr@chromium.org

[davve, 2015-05-29 14:16:16]

PTAL. Not sure who wants to review this so feel free to pass on to others.

[pdr., 2015-06-02 01:41:50]

pdr@chromium.org changed reviewers:
+ chrishtr@chromium.org

[pdr., 2015-06-02 01:41:51]

LGTM, I'm sorry for not getting to this before
https://codereview.chromium.org/1162863006 landed.

https://codereview.chromium.org/1164573003/diff/1/Source/core/paint/NinePiece...
File Source/core/paint/NinePieceImagePainter.h (right):

https://codereview.chromium.org/1164573003/diff/1/Source/core/paint/NinePiece...
Source/core/paint/NinePieceImagePainter.h:20: class NinePieceImagePainter {
Can you add STACK_ALLOCATED() here?

https://codereview.chromium.org/1164573003/diff/1/Source/core/paint/NinePiece...
Source/core/paint/NinePieceImagePainter.h:24: bool paint(GraphicsContext*, const
LayoutRect&, const ComputedStyle&, const NinePieceImage&, SkXfermode::Mode);
Can you make this const?

Maybe best for a followup but can we refactor this to not return a bool? It only
appears to be used in one questionable-looking place with the comment
"border-image is not affected by border-radius."

https://codereview.chromium.org/1164573003/diff/1/Source/core/paint/NinePiece...
Source/core/paint/NinePieceImagePainter.h:27: static LayoutUnit
computeBorderImageSide(const BorderImageLength& borderSlice, LayoutUnit
borderSide, LayoutUnit imageSide, LayoutUnit boxExtent);
Nit, maybe for a followup: should these LayoutUnit params be passed as const
references?

[davve, 2015-06-02 07:18:53]

https://codereview.chromium.org/1164573003/diff/1/Source/core/paint/NinePiece...
File Source/core/paint/NinePieceImagePainter.h (right):

https://codereview.chromium.org/1164573003/diff/1/Source/core/paint/NinePiece...
Source/core/paint/NinePieceImagePainter.h:20: class NinePieceImagePainter {
On 2015/06/02 01:41:51, pdr wrote:
> Can you add STACK_ALLOCATED() here?

Done.

https://codereview.chromium.org/1164573003/diff/1/Source/core/paint/NinePiece...
Source/core/paint/NinePieceImagePainter.h:24: bool paint(GraphicsContext*, const
LayoutRect&, const ComputedStyle&, const NinePieceImage&, SkXfermode::Mode);
On 2015/06/02 01:41:50, pdr wrote:
> Can you make this const?
> 
> Maybe best for a followup but can we refactor this to not return a bool? It
only
> appears to be used in one questionable-looking place with the comment
> "border-image is not affected by border-radius."

Done.

https://codereview.chromium.org/1164573003/diff/1/Source/core/paint/NinePiece...
Source/core/paint/NinePieceImagePainter.h:27: static LayoutUnit
computeBorderImageSide(const BorderImageLength& borderSlice, LayoutUnit
borderSide, LayoutUnit imageSide, LayoutUnit boxExtent);
On 2015/06/02 01:41:51, pdr wrote:
> Nit, maybe for a followup: should these LayoutUnit params be passed as const
> references?

Will look into it in a follow-up.

[davve, 2015-06-02 07:19:08]

The CQ bit was checked by davve@opera.com

[davve, 2015-06-02 07:19:08]

The patchset sent to the CQ was uploaded after l-g-t-m from pdr@chromium.org
Link to the patchset: https://codereview.chromium.org/1164573003/#ps20001
(title: "Address review comments")

[commit-bot: I haz the power, 2015-06-02 07:19:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1164573003/20001

[commit-bot: I haz the power, 2015-06-02 09:00:31]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=196301

[chrishtr, 2015-06-02 15:39:19]

LGTM also. Thanks for improving this code.