By the October deadline discussed offline, the engine should work as follows on iOS:

• On iOS hardware, the engine flag to disable Impeller will be ignored, and the parts of Skia that are no longer needed will not be included in the binary.
• On iOS simulator, the engine flag to disable Impeller will be ignored, but when Metal API access is not available, the engine will fall back to Skia, which will still be included in the binary.

cc @jtmcdole @chinmaygarde @jonahwilliams