Google continues to improve support for RAW images in the newer builds of Chrome OS dev channel.
Googler François Beaufort highlighted the latest improvements:
According to the source code², ARW, CR2, DNG, NEF, NRW, ORF, RAF and RW2 files are the first ones to be editable directly from the Gallery App. For info, it actually converts back to JPG compressed format when you edit the RAW image. Note that the PNaCl³ module responsible for decoding RAW files is called PiexLoader and is only enabled for Google Chrome OS, not chromium build.