thumbnail: Check shm size before writing to it
The SHM is created by the application, which might've done a different size calculation. Verify that the data fits instead of writing past the end and crashing. CCBUG: 430862
The SHM is created by the application, which might've done a different size calculation. Verify that the data fits instead of writing past the end and crashing. CCBUG: 430862
mentioned in commit a288a7ba
·mentioned in commit a288a7ba