Steps to reproduce:

Important: Only reproducible Unity Free ("-force-free)" or with non-Pro mobile addons (when switched to that platform mode).

1. Create new Unity project
2. Select the '2 by 3' layout for better observation of the bug
3. Add a plane to the scene (GameObject -> 3D Object -> Plane)
4. Change the camera position to 0, 3, -10 and rotation to 10, 0, 0
5. Switch the platform to Android or iOS (File -> Build Settings -> Android/iOS -> Switch Platform)
6. Notice the black (sometimes gray) rendered shadow on the game view and Camera Preview window. Also notice that it's shape is exactly the same as what you see in scene view. (For better understanding see this: http://gyazo.com/497de37ce65b96a143e64dde76292abf )
7. Disable the shadows in quality settings (Edit -> Project Settings -> Quality)
8. Notice the absence of the bug