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

third_party/yasm/yasm_assemble.gni

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # This provides the yasm_assemble() template which uses YASM to assemble
 # assembly files.
 #
 # Files to be assembled with YASM should have an extension of .asm.
 #
 # Parameters
@@ skipping 24 matching lines @@
 # Example
 #
 #   yasm_assemble("my_yasm_target") {
 #     sources = [
 #       "ultra_optimized_awesome.asm",
 #     ]
 #     include_dirs = [ "assembly_include" ]
 #   }
 
 if (is_mac || is_ios) {
-  if (cpu_arch == "x86") {
+  if (current_cpu == "x86") {
     _yasm_flags = [
       "-fmacho32",
       "-m",
       "x86",
     ]
-  } else if (cpu_arch == "x64") {
+  } else if (current_cpu == "x64") {
     _yasm_flags = [
       "-fmacho64",
       "-m",
       "amd64",
     ]
   }
 } else if (is_posix) {
-  if (cpu_arch == "x86") {
+  if (current_cpu == "x86") {
     _yasm_flags = [
       "-felf32",
       "-m",
       "x86",
     ]
-  } else if (cpu_arch == "x64") {
+  } else if (current_cpu == "x64") {
     _yasm_flags = [
       "-DPIC",
       "-felf64",
       "-m",
       "amd64",
     ]
   }
 } else if (is_win) {
-  if (cpu_arch == "x86") {
+  if (current_cpu == "x86") {
     _yasm_flags = [
       "-DPREFIX",
       "-fwin32",
       "-m",
       "x86",
     ]
-  } else if (cpu_arch == "x64") {
+  } else if (current_cpu == "x64") {
     _yasm_flags = [
       "-fwin64",
       "-m",
       "amd64",
     ]
   }
 }
 
 if (is_win) {
   asm_obj_extension = "obj"
 } else {
   asm_obj_extension = "o"
 }
 
 template("yasm_assemble") {
   # TODO(ajwong): Support use_system_yasm.
   assert(defined(invoker.sources), "Need sources defined for $target_name")
 
   # Only depend on YASM on x86 systems. Force compilation of .asm files for
   # ARM to fail.
-  assert(cpu_arch == "x86" || cpu_arch == "x64")
+  assert(current_cpu == "x86" || current_cpu == "x64")
 
   action_name = "${target_name}_action"
   source_set_name = target_name
 
   action_foreach(action_name) {
     # Only the source set can depend on this.
     visibility = [ ":$source_set_name" ]
 
     script = "//third_party/yasm/run_yasm.py"
     sources = invoker.sources
@@ skipping 81 matching lines @@
       visibility = invoker.visibility
     }
 
     sources = get_target_outputs(":$action_name")
 
     deps = [
       ":$action_name",
     ]
   }
 }