Reimplement NV21ToARGB to allow different color matrix.

include/libyuv/scale_row.h

Index: include/libyuv/scale_row.h
diff --git a/include/libyuv/scale_row.h b/include/libyuv/scale_row.h
index 30f3cdc571b715f084b875576d68aea4619a2daf..d198addfdde2ae99d3b6e07d1ac3830719571ad2 100644
--- a/include/libyuv/scale_row.h
+++ b/include/libyuv/scale_row.h
@@ -24,11 +24,12 @@ extern "C" {
 #define LIBYUV_DISABLE_X86
 #endif
 
-// Visual C 2012 required for AVX2.
-#if defined(_M_IX86) && !defined(__clang__) && \
-    defined(_MSC_VER) && _MSC_VER >= 1700
-#define VISUALC_HAS_AVX2 1
-#endif  // VisualStudio >= 2012
+// GCC >= 4.7.0 required for AVX2.
+#if defined(__GNUC__) && (defined(__x86_64__) || defined(__i386__))
+#if (__GNUC__ > 4) || (__GNUC__ == 4 && (__GNUC_MINOR__ >= 7))
+#define GCC_HAS_AVX2 1
+#endif  // GNUC >= 4.7
+#endif  // __GNUC__
 
 // clang >= 3.4.0 required for AVX2.
 #if defined(__clang__) && (defined(__x86_64__) || defined(__i386__))
@@ -37,6 +38,12 @@ extern "C" {
 #endif  // clang >= 3.4
 #endif  // __clang__
 
+// Visual C 2012 required for AVX2.
+#if defined(_M_IX86) && !defined(__clang__) && \
+    defined(_MSC_VER) && _MSC_VER >= 1700
+#define VISUALC_HAS_AVX2 1
+#endif  // VisualStudio >= 2012
+
 // The following are available on all x86 platforms:
 #if !defined(LIBYUV_DISABLE_X86) && \
     (defined(_M_IX86) || defined(__x86_64__) || defined(__i386__))
@@ -56,10 +63,17 @@ extern "C" {
 #define HAS_SCALEADDROW_SSE2
 #endif
 
+// The following are available on all x86 platforms, but
+// require VS2012, clang 3.4 or gcc 4.7.
+// The code supports NaCL but requires a new compiler and validator.
+#if !defined(LIBYUV_DISABLE_X86) && (defined(VISUALC_HAS_AVX2) || \
+    defined(CLANG_HAS_AVX2) || defined(GCC_HAS_AVX2))
+#define HAS_SCALEADDROW_AVX2
+#endif
+
 // The following are available for Visual C and clangcl 32 bit:
 #if !defined(LIBYUV_DISABLE_X86) && defined(_M_IX86) && \
     (defined(VISUALC_HAS_AVX2) || defined(CLANG_HAS_AVX2))
-#define HAS_SCALEADDROW_AVX2
 #define HAS_SCALEROWDOWN2_AVX2
 #define HAS_SCALEROWDOWN4_AVX2
 #endif