Limit mp4 atom size to something reasonable am: 638c99ba am: 569f3db6 am:...

Limit mp4 atom size to something reasonable am: 638c99ba am: 569f3db6 am: 29ccd8c5  -s ours am: 03bee198 am: 6c6dd8d9 am: e936431c am: fbd7146f am: e41bf03b am: 8b4b1cab am: 928bcad9 am: 548ad5e1 am: 130dbfb6 am: d5ec68c3 am: a6836b5e am: efa70b01
am: 76107c69

Change-Id: I4aed6c6167160d329a1493e961125f83945ceab9