Use expression functions when appropriate

This CL makes functions having a single return
statement expression functions.

These functions are found by the following command
line.

rg --pcre2 -U '^( +)\w.+ fun .+:.+\{\n\s+return.+\n(?:.+\n)*\1\}' -g '**/desktopmode/**'

Bug: None
Test: None
Flag: EXEMPT format only changes
Change-Id: If3e95c12231aa7cf69dfd60fb9277677a13d25a0