Lift MEDIA_MMX_INTRINSICS_AVAILABLE definition to header and use it to condition media_unittests

media/base/yuv_convert.h

Index: media/base/yuv_convert.h
diff --git a/media/base/yuv_convert.h b/media/base/yuv_convert.h
index 719e6a34abd1edd963ba38ac9a22e758100fa250..30c07abf683831759307d60dfd2322060b94e73b 100644
--- a/media/base/yuv_convert.h
+++ b/media/base/yuv_convert.h
@@ -7,6 +7,16 @@
 
 #include "base/basictypes.h"
 
+// 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
+
 namespace media {
 
 // Type of YUV surface.