Web Inspector: add memory instrumentation for ImageLoader
https://bugs.webkit.org/show_bug.cgi?id=112115

Reviewed by Alexander Pavlov.

Added memory instrumentation to ImageLoader. CachedImage referenced
by the loader is reported as having retaining reference. This allows
to see in the native memory graph CachedImages that are not reachable
from MemoryCache but referenced by HTMLImageElement.

* loader/ImageLoader.cpp:
(WebCore::ImageLoader::reportMemoryUsage):
(WebCore):
* loader/ImageLoader.h:
(ImageLoader):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@145501 268f45cc-cd09-0410-ab3c-d52691b4dbfc