26133 Revert “SceneBuilder.addPicture returns the layer” (cla: yes, waiting for tree to go green, platform-web)

26134 Reland “Fix a11y placeholder on desktop; auto-enable engine semantics” (cla: yes, platform-web)

26139 Move CanvasKit files from parts to libraries (cla: yes, platform-web)

26164 Let the framework toggle between single- and multi-entry histories (cla: yes, waiting for tree to go green, platform-web)

26227 Fix CanvasKit SVG clipPath leak (cla: yes, platform-web, cp: 2.2)

26233 plumb frame number through to framework (cla: yes, waiting for tree to go green, platform-web)

26238 fix mobile a11y placeholder (cla: yes, waiting for tree to go green, platform-web)