Cleanup: Remove unneeded media/ SSE2 checks and unused code. (try 2)

media/base/BUILD.gn

Index: media/base/BUILD.gn
diff --git a/media/base/BUILD.gn b/media/base/BUILD.gn
index 37455d19bd28f942a3afb37a907109b9173007a2..ef87c3246f25c90fc3648bdd58d6bc3f8320ff68 100644
--- a/media/base/BUILD.gn
+++ b/media/base/BUILD.gn
@@ -209,7 +209,6 @@ source_set("base") {
     sources += [ "simd/convert_yuv_to_rgb_x86.cc" ]
     deps += [
       ":media_yasm",
-      ":media_mmx",
       ":media_sse2",
     ]
   }
@@ -351,14 +350,6 @@ source_set("perftests") {
 }
 
 if (cpu_arch == "x86" || cpu_arch == "x64") {
-  source_set("media_mmx") {
-    sources = [ "simd/filter_yuv_mmx.cc" ]
-    configs += [ "//media:media_config" ]
-    if (!is_win) {
-      cflags = [ "-mmmx" ]
-    }
-  }
-
   source_set("media_sse2") {
     sources = [
       "simd/convert_rgb_to_yuv_sse2.cc",
@@ -375,7 +366,6 @@ if (cpu_arch == "x86" || cpu_arch == "x64") {
   yasm_assemble("media_yasm") {
     sources = [
       "simd/convert_rgb_to_yuv_ssse3.asm",
-      "simd/convert_yuv_to_rgb_mmx.asm",
       "simd/convert_yuv_to_rgb_sse.asm",
       "simd/convert_yuva_to_argb_mmx.asm",
       "simd/empty_register_state_mmx.asm",