Duplicate prototype for I420ToABGR for remoting

Add alias prototype in convert_argb.h for remoting to build without the header convert_from.h

BUG=libyuv:622
TBR=harryjin@google.com

Review URL: https://codereview.chromium.org/2141923005 .

include/libyuv/convert_argb.h

@@ -42,6 +42,14 @@ int I420ToARGB(const uint8* src_y, int src_stride_y,
                uint8* dst_argb, int dst_stride_argb,
                int width, int height);
 
+// Duplicate prototype for function in convert_from.h for remoting.
+LIBYUV_API
+int I420ToABGR(const uint8* src_y, int src_stride_y,
+               const uint8* src_u, int src_stride_u,
+               const uint8* src_v, int src_stride_v,
+               uint8* dst_argb, int dst_stride_argb,
+               int width, int height);
+
 // Convert I422 to ARGB.
 LIBYUV_API
 int I422ToARGB(const uint8* src_y, int src_stride_y,