RenderImageResourceStyleImage::image() should return the nullImage() if the image...

RenderImageResourceStyleImage::image() should return the nullImage() if the image is not available
https://bugs.webkit.org/show_bug.cgi?id=174874
<rdar://problem/33530130>

Patch by Said Abou-Hallawa <sabouhallawa@apple.com> on 2017-08-04
Reviewed by Simon Fraser.

Source/WebCore:

If an <img> element has a non-CachedImage content data, e.g. -webkit-named-image,
RenderImageResourceStyleImage will be created and  attached to the RenderImage.
RenderImageResourceStyleImage::m_cachedImage will be set to null at the
beginning because the m_styleImage->isCachedImage() is false in this case.
When ImageLoader finishes loading the url of the src attribute,
RenderImageResource::setCachedImage() will be called to set m_cachedImage.

A crash will happen when the RenderImage is destroyed. Destroying the
RenderImage calls RenderImageResourceStyleImage::shutdown() which checks
m_cachedImage and finds it not null, so it calls RenderImageResourceStyleImage::image()
which ends up calling CSSNamedImageValue::image() which returns a null pointer
because the size is empty. RenderImageResourceStyleImage::shutdown() calls
image()->stopAnimation() without checking the return value of image().

Another crash will happen later when deleting the CachedImage from the memory
cache if CachedImage::canDestroyDecodedData() is called because the client
it gets from m_clients is a freed pointer. This happens because RenderImageResourceStyleImage
has m_styleImage of type StyleGeneratedImage but its m_cachedImage is set
by RenderImageResource::setCachedImage(). When RenderImageResourceStyleImage::shutdown()
is called, it calls  StyleGeneratedImage::removeClient() which does not
know anything about RenderImageResourceStyleImage::m_cachedImage. So we
end up having a freed pointer in the m_clients of the CachedImage.

Test: fast/images/image-element-image-content-data.html

* rendering/RenderImageResourceStyleImage.cpp:
(WebCore::RenderImageResourceStyleImage::shutdown):  Revert back the changes
of r208511 in this function. Add a call to image()->stopAnimation() without
checking the return of image() since it will return the nullImage() if
the image not available. There is no need to check m_cachedImage before
calling image() because image() does not check or access m_cachedImage.

If m_styleImage is not a CachedStyleImage but m_cachedImage is not null,
we need to remove m_renderer from the set of the clients of this m_cachedImage.

(WebCore::RenderImageResourceStyleImage::image const): The base class method
RenderImageResource::image() returns the nullImage() if the image not
available. This is because CachedImage::imageForRenderer() returns
the nullImage() if the image is not available; see CachedImage.h. We should
do the same for the derived class for consistency.

LayoutTests:

* fast/images/image-element-image-content-data-expected.txt: Added.
* fast/images/image-element-image-content-data.html: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@220289 268f45cc-cd09-0410-ab3c-d52691b4dbfc