Fix source buffer selection

This patch fixes a bug in the interaction between the recode loop and
spatial resampling. If the codec was in a spatial resampling state,
and a subsequent iteration of the recode loop disables resampling,
then the source buffer must be reset to the unscaled source.

Change-Id: I4e4cd47b943f6cd26a47449dc7f4255b38e27c77

vp8/encoder/onyx_if.c

@@ -2594,6 +2594,8 @@ static void scale_and_extend_source(YV12_BUFFER_CONFIG *sd, VP8_COMP *cpi)
         cpi->Source = &cpi->scaled_source;
 #endif
     }
+    else
+        cpi->Source = sd;
 }