https://bugs.webkit.org/show_bug.cgi?id=124209

Patch by Aloisio Almeida Jr <aloisio.almeida@openbossa.org> on 2013-11-14
Reviewed by Martin Robinson.

To solve the bug #58309 a cairo subsurface is being used to limit the
source image boundaries.
In many cases, when a cairo subsurface is used for drawing an image,
it occurs an image copy, causing performance penalty. In the case of
the function PlatformContextCairo::drawSurfaceToContext, the image
copy always happens.
So, we should use the subsurface only when it's really necessary.
In cases where we're drawing the whole image, the subsurface is
unnecessary.

The proposed patch avoid the use of subsurfaces when sampling the whole
image.

No new tests. It's an enhancement. Already covered by existing tests.

* platform/graphics/cairo/PlatformContextCairo.cpp:
(WebCore::PlatformContextCairo::drawSurfaceToContext):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@159314 268f45cc-cd09-0410-ab3c-d52691b4dbfc