One thing we should be careful about is communicating this to apps clearly, so that they don't end up with multiple Share items.

Should we be doing any checks here in code? (We can look for descriptions that start with "share" and not add it by default maybe? Then that means adding it by default and adding it through the call should be different extras to track it right.) 

Might get tricky if the menu items are localized. Then when it's tested in English it works...

Is there a way we can make sure we have an ACK of new behavior without being too annoying? Bad(?) example: aborting with an error when a CCT is launched and the user hasn't set share menu item visibility.

Approved at UI review as of 7/20.

Strawman:

Deprecate addDefaultShareMenuItem and add setDefaultShareVisibility(boolean visible [true])

On CustomTabsIntent#build, log a warning(?) to the console if setDefaultShareVisibility has not been called: "The Custom Tabs intent builder defaults to building with a default share menu item as of 24.1. The visibility of this menu item can be controlled with setDefaultShareVisibility. See <link to doc>."