https://bugs.webkit.org/show_bug.cgi?id=119955

Reviewed by Darin Adler.

Source/WebCore:

With this patch, CSS can animate from one -webkit-cross-fade
function to another, when the input images are the same in the
same order.

* css/CSSCrossfadeValue.cpp: Added blend function.
(WebCore::blendFunc):
(WebCore::CSSCrossfadeValue::blend):
(WebCore::CSSCrossfadeValue::equals):
(WebCore::CSSCrossfadeValue::equalInputImages):
* css/CSSCrossfadeValue.h: Added save casting functions.
(WebCore::toCSSCrossfadeValue):
* css/CSSValue.h:
(WebCore::CSSValue::isCrossfadeValue):
* page/animation/CSSPropertyAnimation.cpp: Add another condition to
    interpolate between two -webkit-cross-fade functions.
(WebCore::blendFunc):

LayoutTests:

Test interpolation from one cross-fade function to another. Changed pixel test
to a ref test.

* animations/cross-fade-background-image.html:
* animations/cross-fade-background-image-expected.html: Added.
* platform/mac/animations/cross-fade-background-image-expected.png: Removed.
* platform/mac/animations/cross-fade-background-image-expected.txt: Removed.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@155100 268f45cc-cd09-0410-ab3c-d52691b4dbfc