Update Chomium's build files to work w/ latest GN binaries.

media/BUILD.gn

Index: media/BUILD.gn
diff --git a/media/BUILD.gn b/media/BUILD.gn
index f71d6f81192624fccc7bea4718024890b6925d6d..9169c44077334af085849cfcb489afb219637215 100644
--- a/media/BUILD.gn
+++ b/media/BUILD.gn
@@ -20,7 +20,7 @@ config("media_config") {
   if (!media_use_ffmpeg) {
     defines += [ "MEDIA_DISABLE_FFMPEG" ]
   }
-  if (cpu_arch == "arm" && arm_use_neon) {
+  if (current_cpu == "arm" && arm_use_neon) {
     defines += [ "USE_NEON" ]
   }
   if (use_pulseaudio) {
@@ -306,7 +306,7 @@ component("media") {
     }
   }
 
-  if (cpu_arch == "arm" && arm_use_neon) {
+  if (current_cpu == "arm" && arm_use_neon) {
     defines += [ "USE_NEON" ]
   }
 
@@ -347,7 +347,7 @@ component("media") {
     }
   }
 
-  if (cpu_arch != "arm" && is_chromeos) {
+  if (current_cpu != "arm" && is_chromeos) {
     sources += [
       "filters/h264_bitstream_buffer.cc",
       "filters/h264_bitstream_buffer.h",
@@ -602,7 +602,7 @@ test("media_unittests") {
     ]
   }
 
-  if (cpu_arch != "arm" && is_chromeos) {
+  if (current_cpu != "arm" && is_chromeos) {
     sources += [ "filters/h264_bitstream_buffer_unittest.cc" ]
   }
 
@@ -633,7 +633,7 @@ test("media_unittests") {
     ]
   }
 
-  if (is_win && cpu_arch == "x64") {
+  if (is_win && current_cpu == "x64") {
     cflags += [ "/wd4267" ]  # TODO(wolenetz): Fix size_t to int trunctaion in win64. See
                              # http://crbug.com/171009
   }