Bug 976777:  Truncate long source lines in script errors before sending them to the parent process.  r=bent a=1.3t+

This fixes an out-of-memory foreground-tab crash that I could reliably
reproduce on a 256MB Firefox OS phone, and I think also significantly
reduces the number of background tabs I'm seeing killed due to low
memory.
Bug 994889 - Fix how to get video size from OMXCodec r=cajbir a=1.3t+