Investigate top bottlenecks

LIBYUV_DISABLE_AVX2=1 LIBYUV_WIDTH=1280 LIBYUV_HEIGHT=720 LIBYUV_REPEAT=1000 
perf record out/Release/libyuv_unittest --gtest_filter=*
perf report

 13.81%  libyuv_unittest  libyuv_unittest      [.] libyuv::libyuvTest_ScaleTestRoundToByte_Test::T◆
 13.81%  libyuv_unittest  libyuv_unittest      [.] libyuv::libyuvTest_TestRoundToByte_Test::TestBo▒
  4.94%  libyuv_unittest  libyuv_unittest      [.] ScaleAddRow_C                                  ▒
  4.07%  libyuv_unittest  libyuv_unittest      [.] ScaleARGBRowDownEvenBox_SSE2                   ▒
  3.63%  libyuv_unittest  libyuv_unittest      [.] InterpolateRow_SSSE3                           ▒
  3.57%  libyuv_unittest  libyuv_unittest      [.] I422ToARGBMatrixRow_SSSE3                      ▒
  3.06%  libyuv_unittest  libyuv_unittest      [.] ScaleARGBFilterCols_SSSE3                      ▒
  3.02%  libyuv_unittest  libyuv_unittest      [.] ScaleFilterCols_SSSE3                          ▒
  2.63%  libyuv_unittest  libyuv_unittest      [.] ScaleARGBRowDown2Box_SSE2                      ▒
  2.58%  libyuv_unittest  libyuv_unittest      [.] libyuv::ScaleARGB(unsigned char const*, int, in▒
  2.57%  libyuv_unittest  libyuv_unittest      [.] ARGBToRGB565DitherRow_C                        ▒
  2.45%  libyuv_unittest  libyuv_unittest      [.] ScaleARGBCols_SSE2                             ▒
  2.44%  libyuv_unittest  libc-2.19.so         [.] __random_r                                     ▒
  2.23%  libyuv_unittest  libyuv_unittest      [.] CopyRow_ERMS                                   ▒
  1.64%  libyuv_unittest  libyuv_unittest      [.] I422ToABGRMatrixRow_SSSE3                      ▒
  1.46%  libyuv_unittest  libyuv_unittest      [.] ScaleARGBRowDownEven_SSE2                      ▒
  1.29%  libyuv_unittest  libyuv_unittest      [.] FixedDiv_X86                                   ▒
  1.26%  libyuv_unittest  libyuv_unittest      [.] libyuv::ScaleAddCols1_C(int, int, int, int, uns▒
  1.24%  libyuv_unittest  libyuv_unittest      [.] ARGBShuffleRow_SSSE3                           ▒
  1.21%  libyuv_unittest  libyuv_unittest      [.] CumulativeSumToAverageRow_SSE2                 ▒
  1.14%  libyuv_unittest  libc-2.19.so         [.] __random                                       ▒
  1.08%  libyuv_unittest  libyuv_unittest      [.] ScaleCols_C                                    ▒
  0.99%  libyuv_unittest  libyuv_unittest      [.] ARGBToYRow_SSSE3                               ▒
  0.75%  libyuv_unittest  libyuv_unittest      [.] ComputeCumulativeSumRow_SSE2                   ▒
  0.75%  libyuv_unittest  libc-2.19.so         [.] _int_malloc