fb62aa5d47
Changes the following shell callbacks to flush the dart event loop: * OnPlatformViewSetViewportMetrics * OnPlatformViewDispatchPointerDataPacket * OnPlatformViewDispatchPlatformMessage * OnPlatformViewSetSemanticsEnabled * OnPlatformViewSetAccessibilityFeatures Using a new TaskRunner API RunNowAndFlushMessages. If the task runner can run tasks on the current thread, this will immediately invoke a callback and then post an empty task to the event loop to ensure dart listeners fire. Unlike https://github.com/flutter/engine/pull/56738, does not touch the vsync API - which looks like it depends on scheduling behavior today, at least for iOS.