Moi - working on my app I added an emulator for api 18 to go along with 17 and 16. FYI, I am emulating an N7.
All is well and consistent for 16 and 17. However, wtf with 18. My application title and its icon seem to be put in a layout slightly larger. This is noticable as the default application background overlays the light blue border I've tried to compare to screen captures and as best I can tell the placement of the icon and application title text are identical but the background extends an extra 4 or 5 pixels.
Has anyone else had this issue? TIA
To try to make things a bit more obvious I changed the application base theme to Holo.Light. On API 17, the application background color only shows behind the icon and the app name text. However, on API 18 the background covers a rectangular area the height of the title/action bar and slightly wider than the icon and title. My only styling (to this point) is
<style name="AppBaseTheme" parent="android:Theme.Holo">
<item name="android:background">#FF000024</item>
</style>
The desired behavior is that API 18 Holo (dark) looks the same as API 17 and 16.
API 17 Light 
API 17 Dark 
API 18 Dark 
API 18 Light 
More info: I've used the android debug tools to verify that the actual layout element sizes are identical on api 16/17/18/19. However, API 18 and 19 have this issue with the background in the lanuncer icon area (android:id/home).