Exclude Clang on Windows too. Comment this up a bit.

src/opts/SkBlitRow_opts_SSE4.h

 /*
  * Copyright 2014 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkBlitRow_opts_SSE4_DEFINED
 #define SkBlitRow_opts_SSE4_DEFINED
 
 #include "SkBlitRow.h"
 
-/* Check if we are able to build assembly code, GCC/AT&T syntax.
- * Had problems with LLVM-GCC 4.2.
- * MemorySanitizer cannot handle assembly code.
+/* 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 (defined(__clang__) || (defined(__GNUC__) && !defined(SK_BUILD_FOR_MAC))) \
-    && !defined(MEMORY_SANITIZER)
+#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