libvpx: Pull from upstream

source/libvpx/vp9/common/vp9_idct.h

Index: source/libvpx/vp9/common/vp9_idct.h
===================================================================
--- source/libvpx/vp9/common/vp9_idct.h	(revision 290053)
+++ source/libvpx/vp9/common/vp9_idct.h	(working copy)
@@ -81,6 +81,16 @@
 
 static INLINE int dct_const_round_shift(int input) {
   int rv = ROUND_POWER_OF_TWO(input, DCT_CONST_BITS);
+#if CONFIG_COEFFICIENT_RANGE_CHECKING
+  // For valid VP9 input streams, intermediate stage coefficients should always
+  // stay within the range of a signed 16 bit integer. Coefficients can go out
+  // of this range for invalid/corrupt VP9 streams. However, strictly checking
+  // this range for every intermediate coefficient can burdensome for a decoder,
+  // therefore the following assertion is only enabled when configured with
+  // --enable-coefficient-range-checking.
+  assert(INT16_MIN <= rv);
+  assert(rv <= INT16_MAX);
+#endif
   return (int16_t)rv;
 }