Previously, SkTextBlob was built on every paint in
DisplayListPlayerSkia::draw_glyph_run(), which meant:
- Repeated work when the same display list is painted multiple times
- Glyph arrays were allocated and populated on each paint
Now the blob is built once during display list recording and cached in
GlyphRun.
Move the visual viewport (pinch-to-zoom) transform from a reserved slot
in DisplayList to the AccumulatedVisualContext tree as a root transform
node. Fixed position elements now correctly inherit from this context.
This requires rebuilding the context tree and display list on each zoom
change, but this overhead will be eliminated by future partial context
tree rebuilds.
AccumulatedVisualContext nodes capture a snapshot of the current clip
rect when the tree is built, so we must invalidate whenever the clip
property changes.
This test verifies that modifying the CSS clip property via JavaScript
properly invalidates the accumulated visual context. Currently fails
because the clip rect in the display list remains unchanged after the
style update.
