Cast for clang-cl 64 bit build warnings in unittests

unit_test/convert_test.cc

 /*
  *  Copyright 2011 The LibYuv Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS. All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 1999 matching lines @@
   }                                                                            \
   memset(dst_argb_b + OFF, 1, kStrideB * kHeight);                             \
   for (int i = 0; i < benchmark_iterations_; ++i) {                            \
     FMT_PLANAR##To##FMT_B(src_y + OFF, kWidth,                                 \
                           src_u + OFF, SUBSAMPLE(kWidth, SUBSAMP_X),           \
                           src_v + OFF, SUBSAMPLE(kWidth, SUBSAMP_X),           \
                           src_a + OFF, kWidth,                                 \
                           dst_argb_b + OFF, kStrideB,                          \
                           kWidth, NEG kHeight, ATTEN);                         \
   }                                                                            \
-  int max_diff = 0;                                                            \
   /* Convert to a 3rd format in 1 step and 2 steps and compare  */             \
   const int kStrideC = kWidth * BPP_C;                                         \
   align_buffer_page_end(dst_argb_c, kStrideC * kHeight + OFF);                 \
   align_buffer_page_end(dst_argb_bc, kStrideC * kHeight + OFF);                \
   memset(dst_argb_c + OFF, 2, kStrideC * kHeight);                             \
   memset(dst_argb_bc + OFF, 3, kStrideC * kHeight);                            \
   FMT_PLANAR##To##FMT_C(src_y + OFF, kWidth,                                   \
                         src_u + OFF, SUBSAMPLE(kWidth, SUBSAMP_X),             \
                         src_v + OFF, SUBSAMPLE(kWidth, SUBSAMP_X),             \
                         src_a + OFF, kWidth,                                   \
@@ skipping 25 matching lines @@
         benchmark_width_, _Invert, -, 0, FMT_C, BPP_C, 0)                      \
     TESTQPLANARTOEI(FMT_PLANAR, SUBSAMP_X, SUBSAMP_Y, FMT_B, SUB_B, BPP_B,     \
         benchmark_width_, _Opt, +, 0, FMT_C, BPP_C, 0)                         \
       TESTQPLANARTOEI(FMT_PLANAR, SUBSAMP_X, SUBSAMP_Y, FMT_B, SUB_B, BPP_B,   \
           benchmark_width_, _Premult, +, 0, FMT_C, BPP_C, 1)
 
 TESTQPLANARTOE(I420Alpha, 2, 2, ARGB, 1, 4, ABGR, 4)
 TESTQPLANARTOE(I420Alpha, 2, 2, ABGR, 1, 4, ARGB, 4)
 
 }  // namespace libyuv