Remove old references to cpu_arch, os from GN files.

build/config/BUILDCONFIG.gn

Index: build/config/BUILDCONFIG.gn
diff --git a/build/config/BUILDCONFIG.gn b/build/config/BUILDCONFIG.gn
index 8e30c4a0a3e62ff6780afc9fdd086d06cd644694..455ec0d3dc4bebd3cee1b670fe5c87c277c99bfb 100644
--- a/build/config/BUILDCONFIG.gn
+++ b/build/config/BUILDCONFIG.gn
@@ -17,27 +17,12 @@
 # Use "is_*" names for intrinsic platform descriptions and build modes, and
 # "use_*" names for optional features libraries, and configurations.
 
-# TODO(dpranke): The os and cpu_arch variables exist for backwards
-# compatibility and should be deleted once all of the build files and
-# bots have been updated to use current_cpu/target_cpu and
-# current_os/target_os instead.
-
 if (target_os == "") {
-  if (defined(os)) {
-    # If os is defined, it was set in an args file and needs to be
-    # used for backwards-compatibility.
-    target_os = os
-  } else {
-    target_os = host_os
-  }
+  target_os = host_os
 }
 
 if (target_cpu == "") {
-  if (defined(cpu_arch)) {
-    # If cpu_arch is defined, it was set in an args file and needs to be
-    # used for backwards-compatibility.
-    target_cpu = cpu_arch
-  } else if (target_os == "android") {
+  if (target_os == "android") {
     # If we're building for Android, we should assume that we want to
     # build for ARM by default, not the host_cpu (which is likely x64).
     # This allows us to not have to specify both target_os and target_cpu
@@ -56,13 +41,6 @@ if (current_os == "") {
 }
 
 declare_args() {
-  # TODO(dpranke): These values are here for backwards compatibility and
-  # should be deleted when all of the builders and configs have been updated.
-  cpu_arch = target_cpu
-  os = target_os
-  build_cpu_arch = host_cpu
-  build_os = host_os
-
   # How many symbols to include in the build. This affects the performance of
   # the build since the symbols are large and dealing with them is slow.
   #   2 means regular build with symbols.
@@ -115,10 +93,6 @@ declare_args() {
   }
 }
 
-# TODO(dpranke): Remove these asserts when os and cpu_arch are removed.
-assert(current_cpu == cpu_arch)
-assert(current_os == os)
-
 # =============================================================================
 # OS DEFINITIONS
 # =============================================================================
@@ -539,8 +513,8 @@ if (is_win) {
 } else if (is_nacl) {
   # TODO(GYP): This will need to change when we get NaCl working
   # on multiple platforms, but this whole block of code (how we define
-  # host_toolchain) needs to be reworked regardless to key off of build_os
-  # and build_cpu_arch rather than the is_* variables.
+  # host_toolchain) needs to be reworked regardless to key off of host_os
+  # and host_cpu rather than the is_* variables.
   host_toolchain = "//build/toolchain/linux:clang_x64"
 }