Add AnimatedDecodedImageData which implements DecodedImageData with
an 8-slot buffer pool instead of storing all frames in memory.
Frames are requested on demand from the ImageDecoder service as
the animation progresses.
For a 344-frame animated image at 1920x1080, this reduces
WebContent memory from ~1.3 GB to ~66 MB.
The streaming class owns frame progression and synchronizes
multiple callers (HTMLImageElement and ImageStyleValue) through
notify_frame_advanced() returning the authoritative frame index.
When a frame isn't in the pool, the last displayed frame is shown
as a fallback (brief freeze rather than blank).
Rename the old AnimatedBitmapDecodedImageData (which now only
handles static/single-frame images) to BitmapDecodedImageData.
Instead of painting DecodedImageData by first asking it for a bitmap
and then painting that, this commit adds two new APIs:
- frame_rect(frame_index):
Gets the size of the animation frame at the given index.
- paint(context, ...):
Paints the DecodedImageData into a DisplayListRecordingContext.
The main powerful thing here is that this allows SVGDecodedImageData
to render itself using the GPU when available.
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
