Revert of SSE4 opaque blend using intrinsics instead of assembly.

src/opts/SkBlitRow_opts_SSE4.h

Index: src/opts/SkBlitRow_opts_SSE4.h
diff --git a/src/opts/SkBlitRow_opts_SSE4.h b/src/opts/SkBlitRow_opts_SSE4.h
index 577ace6f8fe462a8083b87a75e2faed377fac5b0..600e669893dd32bb156d3b5cfd2686e50eeb715b 100644
--- a/src/opts/SkBlitRow_opts_SSE4.h
+++ b/src/opts/SkBlitRow_opts_SSE4.h
@@ -10,9 +10,24 @@
 
 #include "SkBlitRow.h"
 
-void S32A_Opaque_BlitRow32_SSE4(SkPMColor* SK_RESTRICT,
-                                const SkPMColor* SK_RESTRICT,
-                                int count,
-                                U8CPU alpha);
+#ifdef CRBUG_399842_FIXED
+
+/* Check if we are able to build assembly code, GCC/AT&T syntax:
+ *  1) Clang and GCC are generally OK.  OS X's old LLVM-GCC 4.2 can't handle it;
+ *  2) We're intentionally not linking this in even when supported (Clang) on Windows;
+ *  3) MemorySanitizer cannot instrument assembly at all.
+ */
+#if /* 1)*/ (defined(__clang__) || (defined(__GNUC__) && !defined(SK_BUILD_FOR_MAC))) \
+    /* 2)*/ && !defined(SK_BUILD_FOR_WIN)                                             \
+    /* 3)*/ && !defined(MEMORY_SANITIZER)
+extern "C" void S32A_Opaque_BlitRow32_SSE4_asm(SkPMColor* SK_RESTRICT dst,
+                                               const SkPMColor* SK_RESTRICT src,
+                                               int count, U8CPU alpha);
+
+#define SK_ATT_ASM_SUPPORTED
 #endif
 
+#endif // CRBUG_399842_FIXED
+
+#endif
+