Initial SVG backend stubbing

Initial SVG backend stubbing

This adds SkSVGDevice and a small utility for converting SKP files to SVG (skp2svg).

R=reed@google.com,jcgregorio@google.com
BUG=skia:3368
Committed: https://skia.googlesource.com/skia/+/93957f4e8087774f35e2d1c3ff38ec7da306551d

[f(malita), 2015-01-30 14:50:36]

fmalita@chromium.org changed reviewers:
+ jcgregorio@google.com, reed@google.com

[f(malita), 2015-01-30 15:00:34]

fmalita@chromium.org changed reviewers:
+ caryclark@google.com

[f(malita), 2015-01-30 15:00:34]

Only solid color (transformed) paths and rects are supported atm (OTOH, it's
pretty impressive what one can achieve with paths-only - for example
http://upload.wikimedia.org/wikipedia/commons/f/fd/Ghostscript_Tiger.svg gets
converted perfectly AFAICT :)

[reed1, 2015-01-30 15:59:06]

When we expose this, do you think it is...
- a surface
- a document
- a custom thing (e.g. picturerecorder)
?

[reed1, 2015-01-30 15:59:10]

lgtm

[f(malita), 2015-01-30 16:05:20]

On 2015/01/30 15:59:06, reed1 wrote:
> When we expose this, do you think it is...
> - a surface
> - a document
> - a custom thing (e.g. picturerecorder)
> ?

My first thought was for it to be a canvas, constructed via a specialized
factory (CreateSVGCanvas()?). A surface sounds like a better way to go though
(with a SkSurface::NewSVGWriter() factory).

[mtklein, 2015-01-30 16:14:39]

> My first thought was for it to be a canvas, constructed via a specialized
> factory (CreateSVGCanvas()?). A surface sounds like a better way to go though
> (with a SkSurface::NewSVGWriter() factory).

Seems like it fits the Surface/Image model exactly the same way pictures do...
you can record them, you can snap them off, but they don't naturally have
pixels.

That last bit is the part that's keeping picture recorders and pictures from
being surfaces and images in my head.  If we do end up with SVG as surface /
image, let's think about whether pictures are too.

[f(malita), 2015-01-30 16:57:26]

The CQ bit was checked by fmalita@chromium.org

[commit-bot: I haz the power, 2015-01-30 16:57:46]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/892533002/20001

[reed1, 2015-01-30 16:58:10]

I am still good that pictures != surface/image.

I look at PDF, and our decision to make it follow a 3rd factory pattern :
SkDocument/SkPage. Perhaps SVG is a document?

[commit-bot: I haz the power, 2015-01-30 17:03:34]

Committed patchset #2 (id:20001) as
https://skia.googlesource.com/skia/+/93957f4e8087774f35e2d1c3ff38ec7da306551d