to Y,U,V and a pixel stride for U and V.  The pixel stride is expected to be 1 or 2.

[ RUN      ] LibYUVConvertTest.Android420ToI420_1_Any
[       OK ] LibYUVConvertTest.Android420ToI420_1_Any (253 ms)
[ RUN      ] LibYUVConvertTest.Android420ToI420_1_Unaligned
[       OK ] LibYUVConvertTest.Android420ToI420_1_Unaligned (250 ms)
[ RUN      ] LibYUVConvertTest.Android420ToI420_1_Invert
[       OK ] LibYUVConvertTest.Android420ToI420_1_Invert (254 ms)
[ RUN      ] LibYUVConvertTest.Android420ToI420_1_Opt
[       OK ] LibYUVConvertTest.Android420ToI420_1_Opt (247 ms)
[ RUN      ] LibYUVConvertTest.Android420ToI420_2_Any
[       OK ] LibYUVConvertTest.Android420ToI420_2_Any (132 ms)
[ RUN      ] LibYUVConvertTest.Android420ToI420_2_Unaligned
[       OK ] LibYUVConvertTest.Android420ToI420_2_Unaligned (122 ms)
[ RUN      ] LibYUVConvertTest.Android420ToI420_2_Invert
[       OK ] LibYUVConvertTest.Android420ToI420_2_Invert (124 ms)
[ RUN      ] LibYUVConvertTest.Android420ToI420_2_Opt
[       OK ] LibYUVConvertTest.Android420ToI420_2_Opt (119 ms)

TEST=LibYUVConvertTest.Android420ToI420_Opt
BUG=libyuv:604
R=braveyao@chromium.org

Review URL: https://codereview.chromium.org/2146733002 .