https://bugs.webkit.org/show_bug.cgi?id=96135

Reviewed by Adam Barth.

This patch is for preparation of deferred image decoding.
ImageSource will be used as a portal to access deferred image decoder
by BitmapImage, it should not be accessible through WebKit APIs.

WebImage now calls ImageDecoder directly which is the actual
implementation of an image decoder.

Tests: WebImageTest.PNGImage
       WebImageTest.ICOImage

* WebKit.gypi:
* src/WebImageSkia.cpp:
(WebKit::WebImage::fromData):
(WebKit::WebImage::framesFromData):
* tests/WebImageTest.cpp: Added.
(WebKit):
(WebKit::readFile):
(WebKit::TEST):
* tests/data/black-and-white.ico: Added.
* tests/data/white-1x1.png: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@128939 268f45cc-cd09-0410-ab3c-d52691b4dbfc