Lift MEDIA_MMX_INTRINSICS_AVAILABLE definition to header and use it to condition media_unittests

media/base/yuv_convert.cc

Index: media/base/yuv_convert.cc
diff --git a/media/base/yuv_convert.cc b/media/base/yuv_convert.cc
index f32c1d2ff9c292219b029bbaf20e7490f91ead65..85b06995b512f70c2929ad8f28a3ccc50d1ef029 100644
--- a/media/base/yuv_convert.cc
+++ b/media/base/yuv_convert.cc
@@ -33,16 +33,6 @@
 #endif
 #endif
 
-// Visual Studio 2010 does not support MMX intrinsics on x64.
-// Some win64 yuv_convert code paths use SSE+MMX yasm, so without rewriting
-// them, we use yasm EmptyRegisterState_MMX in place of _mm_empty() or
-// hide the versions implemented with heavy use of MMX intrinsics.
-// TODO(wolenetz): Use MMX intrinsics when compiling win64 with Visual
-// Studio 2012? http://crbug.com/173450
-#if !(defined(ARCH_CPU_X86_64) && defined(COMPILER_MSVC))
-#define MEDIA_MMX_INTRINSICS_AVAILABLE
-#endif
-
 // Assembly functions are declared without namespace.
 extern "C" {
 void EmptyRegisterState_MMX();