[CG] Rasterized scaling of transformed SVG shapes with gradient fill and -webkit...

[CG] Rasterized scaling of transformed SVG shapes with gradient fill and -webkit-svg-shadow applied
https://bugs.webkit.org/show_bug.cgi?id=76482
<rdar://problem/10415483>

Reviewed by Simon Fraser.

Scale the CGLayer used when filling or stroking a shadowed path or rect with
a gradient in GraphicsContextCG. Previously, the CGLayer was created and rendered
into at the untransformed size of the shape, leading to pixelation when it was
then scaled up and drawn into the destination.

Add AffineTransform::mapSize() to map a size through a transformation.

Test: svg/custom/transform-with-shadow-and-gradient.svg

* platform/graphics/cg/GraphicsContextCG.cpp:
(WebCore::GraphicsContext::fillPath):
(WebCore::GraphicsContext::strokePath):
(WebCore::GraphicsContext::fillRect):
(WebCore::GraphicsContext::strokeRect):
* platform/graphics/transforms/AffineTransform.cpp:
(WebCore::AffineTransform::mapSize): Added.
* platform/graphics/transforms/AffineTransform.h:

Add a test that ensures that SVG shapes are drawn crisply when transformed
if they have both a gradient fill and -webkit-svg-shadow applied.

* platform/mac/svg/custom/transform-with-shadow-and-gradient-expected.png: Added.
* platform/mac/svg/custom/transform-with-shadow-and-gradient-expected.txt: Added.
* svg/custom/transform-with-shadow-and-gradient.svg: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@105296 268f45cc-cd09-0410-ab3c-d52691b4dbfc