Add MIPS SIMD Arch (MSA) optimized MirrorRow function

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index e2deffafaac2330c80ae97cb46b10035cd820d41..fd8e231270110773c20d38c5a7ad3f4542fc41db 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -94,6 +94,10 @@ static_library("libyuv") {
     deps += [ ":libyuv_neon" ]
   }
 
+  if (libyuv_use_msa) {
+    deps += [ ":libyuv_msa" ]
+  }
+
   if (is_nacl) {
     # Always enable optimization under NaCl to workaround crbug.com/538243 .
     configs -= [ "//build/config/compiler:default_optimization" ]
@@ -124,6 +128,17 @@ if (libyuv_use_neon) {
   }
 }
 
+if (libyuv_use_msa) {
+  static_library("libyuv_msa") {
+    sources = [
+      # MSA Source Files
+      "source/row_msa.cc",
+    ]
+
+    public_configs = [ ":libyuv_config" ]
+  }
+}
+
 if (libyuv_include_tests) {
   config("libyuv_unittest_warnings_config") {
     if (!is_win) {