Chrome Canary now has a flag to enable CSS Exclusions. In Canary, enter “about:flags” in the address bar, find “Enable experimental WebKit features”, click “Enable”, and relaunch Canary.
Note that the implementation of this feature is still in progress, and currently only a subset of shape-inside functionality is available. You can find more information, and demos, on the samples page. Hans Muller has written in much greater detail what shape-inside would allow you to do.
For an explanation of Chrome flags, check out Christian Cantrell’s video.