Propagate the CORS-cross-origin state from image fetch responses through
SharedResourceRequest, ImageRequest, and the available image cache.
Use that state when drawing HTML images to canvas so cross-origin image
data taints the canvas correctly.
Prune decoded image resources retained by active documents once they
grow beyond a recent working set. Route-heavy applications can load
many unique images through one Document, and the shared resource and
available-image caches would otherwise keep decoded image data alive
after the DOM stopped using those images.
Track cache touches and evict least recently used decoded images from
both caches. This keeps active documents from accumulating unbounded
decoded image resources while preserving a small hot cache for repeat
loads.
Both Chromium and Gecko delay the document's load event for CSS image
resource requests (background-image, mask-image, etc). We now start
fetching CSS image resources as soon as their stylesheet is associated
with a document, rather than deferring until layout. This is done by
collecting ImageStyleValues during stylesheet parsing and initiating
their fetches when the stylesheet is added to the document.
Fixes#3448
Resulting in a massive rename across almost everywhere! Alongside the
namespace change, we now have the following names:
* JS::NonnullGCPtr -> GC::Ref
* JS::GCPtr -> GC::Ptr
* JS::HeapFunction -> GC::Function
* JS::CellImpl -> GC::Cell
* JS::Handle -> GC::Root
