[MIPS] Add support for Chromium-Android for MIPS build to BUILD.gn

Fix build regressions for Chrome for Android for MIPS that came with r242674.

BUG= gclient runhooks fails for MIPS
TEST= build content_shell for Android MIPS

Review URL: https://codereview.chromium.org/111633004

git-svn-id: http://src.chromium.org/svn/trunk/src/build@242797 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

gyp_chromium

@@ -138,6 +138,7 @@ def GetArgsStringForGN(supplemental_files):
       ('target_arch', 'ia32', 'cpu_arch="x86"'),
       ('target_arch', 'x64', 'cpu_arch="x64"'),
       ('target_arch', 'arm', 'cpu_arch="arm"'),
+      ('target_arch', 'mipsel', 'cpu_arch="mipsel"'),
       ('fastbuild', '0', 'symbol_level=2'),
       ('fastbuild', '1', 'symbol_level=1'),
       ('fastbuild', '2', 'symbol_level=0'),

toolchain/android/BUILD.gn

@@ -33,6 +33,8 @@ if (is_gyp) {
       android_toolchain_arch = "x86-4.6"
     } else if (cpu_arch == "arm") {
       android_toolchain_arch = "arm-linux-androideabi-4.6"
+    } else if (cpu_arch == "mipsel") {
+      android_toolchain_arch = "mipsel-linux-android-4.6"
     } else {
       assert(false, "Need Android toolchain support for your platform.")
     }
@@ -99,3 +101,14 @@ gcc_toolchain("arm") {
   toolchain_cpu_arch = "arm"
   toolchain_os = "android"
 }
+
+gcc_toolchain("mipsel") {
+  prefix = "$android_ndk_root/toolchains/mipsel-linux-android-4.6/prebuilt/$build_os-$android_host_arch/bin/mipsel-linux-android-"
+  cc  = prefix + "gcc"
+  cxx = prefix + "g++"
+  ar  = prefix + "ar"
+  ld  = cxx
+
+  toolchain_cpu_arch = "mipsel"
+  toolchain_os = "android"
+}