(1) upgrade the 62 project the 70 sdk project,
(2) switch to "upgrade descriptor files" page
(3) notice the there are no files about theme project then click "upgrade" button.
(4) then upgrade the 70 sdk project to liferay-workspace and switch to "upgrade descriptor files" page
(5) notice the liferay-look-and-feel.xml from theme project and some files from the directory plugins-sdk/tools can be found.
upgrade 62 sdk to 70 project :the theme project is filtered.
but when upgrade the maven project :the theme proejct isn't filtered.