Fix ext-tx experiment for highbitdepth
Fix ext-tx experiment for highbitdepth

Change-Id: I610e18f150d73378283882ae81f5f77c367d2956

luctrudeau/aom,mbebenita/aom,luctrudeau/aom,mbebenita/aom,smarter/aom,smarter/aom,mbebenita/aom,GrokImageCompression/aom,luctrudeau/aom,smarter/aom,mbebenita/aom,smarter/aom,luctrudeau/aom,GrokImageCompression/aom,mbebenita/aom,mbebenita/aom,luctrudeau/aom,mbebenita/aom,smarter/aom,GrokImageCompression/aom,mbebenita/aom,GrokImageCompression/aom,GrokImageCompression/aom,smarter/aom,mbebenita/aom,luctrudeau/aom,GrokImageCompression/aom