Fix the GN build for MIPS.

BUILD.gn

 # 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.
 
 import("//build/config/android/config.gni")
 import("//build/config/arm.gni")
 import("//build/config/mips.gni")
 
 # Because standalone V8 builds are not supported, assume this is part of a
 # Chromium build.
@@ skipping 95 matching lines @@
     defines += [ "V8_USE_EXTERNAL_STARTUP_DATA" ]
   }
 }
 
 config("toolchain") {
   visibility = [ ":*" ]  # Only targets in this file can depend on this.
 
   defines = []
   cflags = []
 
-  # TODO(jochen): Add support for arm subarchs, mips, mipsel.
+  # TODO(jochen): Add support for arm subarchs, mips, mipsel, mips64el.

[Dirk Pranke, 2015/03/17 21:44:13]

I think this is completely appropriate. 

lgtm.

 
   if (v8_target_arch == "arm") {
     defines += [ "V8_TARGET_ARCH_ARM" ]
     if (current_cpu == "arm") {
       if (arm_version == 7) {
         defines += [ "CAN_USE_ARMV7_INSTRUCTIONS" ]
       }
       if (arm_fpu == "vfpv3-d16") {
         defines += [ "CAN_USE_VFP3_INSTRUCTIONS" ]
       } else if (arm_fpu == "vfpv3") {
@@ skipping 16 matching lines @@
         "CAN_USE_VFP32DREGS",
         "USE_EABI_HARDFLOAT=0",
       ]
     }
 
     # TODO(jochen): Add support for arm_test_noprobe.
   }
   if (v8_target_arch == "arm64") {
     defines += [ "V8_TARGET_ARCH_ARM64" ]
   }
+  if (v8_target_arch == "mipsel") {
+    defines += [ "V8_TARGET_ARCH_MIPS" ]
+  }
+  if (v8_target_arch == "mips64el") {
+    defines += [ "V8_TARGET_ARCH_MIPS64" ]
+  }
   if (v8_target_arch == "x86") {
     defines += [ "V8_TARGET_ARCH_IA32" ]
   }
   if (v8_target_arch == "x64") {
     defines += [ "V8_TARGET_ARCH_X64" ]
   }
   if (is_win) {
     defines += [ "WIN32" ]
     # TODO(jochen): Support v8_enable_prof.
   }
@@ skipping 1421 matching lines @@
       sources += [
         "src/d8-debug.cc",
         "$target_gen_dir/d8-js.cc",
       ]
     }
     if (v8_enable_i18n_support) {
       deps += [ "//third_party/icu" ]
     }
   }
 }