Decoded image data should not continue to traffic in ImmutableBitmap now
that the bitmap wrapper is being retired. Introduce DecodedImageFrame as
the paintable decoded-image unit and store a Bitmap plus ColorSpace in
it directly.
Thread the new frame type through decoded image data, display-list
image commands, filters, canvas drawImage, patterns, WebGL texture
upload, and CSS/SVG image consumers. ImmutableBitmap remains only at
the legacy boundaries that still need it, such as HTML video snapshots
and callers that explicitly ask for a bitmap snapshot.
This keeps color-space ownership with the decoded frame while making
the expensive or legacy ImmutableBitmap path explicit at the few call
sites that still need it.
Decoded video frames should own their planar YUV data and color space
directly. Keeping that storage behind ImmutableBitmap gave a
still-image abstraction media-specific behavior and made calls like
bitmap() potentially allocate and convert a whole video frame.
Move YUV ownership into Media::VideoFrame, where the lifetime naturally
follows media playback, and remove the YUV-backed mode from
ImmutableBitmap. This commit intentionally keeps the visible Web paint
path on ExternalContentSource by converting the current frame back to
an ImmutableBitmap where Web still expects one.
Callers that need pixels now ask the frame to convert explicitly. That
preserves behavior for canvas and bitmap consumers while making the
expensive YUV-to-pixel path visible at the call site instead of
hiding it behind ImmutableBitmap::bitmap().
The previous commit dropped ImmutableBitmap's GPU upload path along with
its Skia metadata, leaving YUV-backed bitmaps falling back to a CPU
bitmap conversion before drawing. Restore the YUV-to-GPU upload inside
the cache so video frames stay as YUV textures on the GPU instead of
being converted to RGBA on the CPU first.
With the SkImage cache extracted, ImmutableBitmap no longer needs to
hold a SkiaBackendContext, an SkImage, or an SkBitmap. Reduce it to just
the source pixels (a Bitmap or YUVData) and a color space, so the sam
ImmutableBitmap can be consumed by any Skia context without
coordination.
Per-context locking and ensure_sk_image() are no longer needed and go
away with this change; the cache rebuilds an SkImage from the source
data the first time each bitmap is drawn against a context.
ImmutableBitmap currently caches an SkImage tied to a specific Skia
backend context, which prevents using the same bitmap with more than one
context. Move that cache out into a per-painter
ImmutableBitmapSkiaImageCache so the cached image lives next to the
context that produced it.
Painters and the display-list player prune their caches each frame, and
canvas 2D contexts prune when presenting, so unused images do not
accumulate.
