This patch fixed the following warning:
src\third_party\libvpx\source\libvpx\vp9\encoder\vp9_pickmode.c(1607) :
warning C6246: Local declaration of 'this_mode' hides declaration of the
same name in outer scope.

Change-Id: I1d93c4a47a13cb13089fec5bd61e8b58e6cd8d58