Add support for building v8 on mips and mips64 using GN.

build/config/mips.gni

 # Copyright 2015 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/v8_target_cpu.gni")
 
 # These are primarily relevant in current_cpu == "mips*" contexts, where
 # MIPS code is being compiled.  But they can also be relevant in the
 # other contexts when the code will change its behavior based on the
 # cpu it wants to generate code for.
-if (current_cpu == "mipsel" || v8_current_cpu == "mipsel") {
+if (current_cpu == "mipsel" || v8_current_cpu == "mipsel" ||
+    current_cpu == "mips" || v8_current_cpu == "mips") {
   declare_args() {
     # MIPS arch variant. Possible values are:
     #   "r1"
     #   "r2"
     #   "r6"
     mips_arch_variant = "r1"
 
     # MIPS DSP ASE revision. Possible values are:
     #   0: unavailable
     #   1: revision 1
     #   2: revision 2
     mips_dsp_rev = 0
 
     # MIPS SIMD Arch compilation flag.
     mips_use_msa = false
 
     # MIPS floating-point ABI. Possible values are:
     #   "hard": sets the GCC -mhard-float option.
     #   "soft": sets the GCC -msoft-float option.
     mips_float_abi = "hard"
 
     # MIPS32 floating-point register width. Possible values are:
     #   "fp32": sets the GCC -mfp32 option.
     #   "fp64": sets the GCC -mfp64 option.
     #   "fpxx": sets the GCC -mfpxx option.
     mips_fpu_mode = "fp32"
   }
-} else if (current_cpu == "mips64el" || v8_current_cpu == "mips64el") {
+} else if (current_cpu == "mips64el" || v8_current_cpu == "mips64el" ||
+           current_cpu == "mips64" || v8_current_cpu == "mips64") {
   # MIPS arch variant. Possible values are:
   #   "r2"
   #   "r6"
   if (current_os == "android" || target_os == "android") {
     declare_args() {
       mips_arch_variant = "r6"
 
       # MIPS SIMD Arch compilation flag.
       mips_use_msa = true
     }
   } else {
     declare_args() {
       mips_arch_variant = "r2"
 
       # MIPS SIMD Arch compilation flag.
       mips_use_msa = false
     }
   }
 }