My video card is ATI hd6470m [Radeon HD 6400M/7400M Series]. The Adobe flash
player was running well before mesaLib-10.0.0. After I updated to 10.0 or 10.1,
the Adobe flash player is always crashed.

I think the problem is at the function called "pipe_context", which is in the
file gallium/drivers/radeonsi/si_pipe.c

Here are some tips to reappear this bug as I meet.
1, Open a terminal, run "firefox -safe-mode".
2, Open a web page with flash player plugin, if it is a video site like
youtube, it is better. (For me, I use http://www.youku.com)
3, Flash player plugin will crash.
4, Goto the terminal, some information is printed. Notice that as below.
   "si_pipe.c: Unsupported chip class 6."

My environment, hd6470m, Arch Linux x86_64, i3_wm
/etc/adobe/mms.cfg:
EnableLinuxHWVideoDecode=1

This bug is on the version 10.0, 10.1 and git master branch(2014-3-11).