Add compiler and linker flags for MIPS.

build/config/compiler/BUILD.gn

 # Copyright (c) 2013 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")
 if (cpu_arch == "arm") {
   import("//build/config/arm.gni")
 }
+if (cpu_arch == "mipsel" || cpu_arch == "mips64el") {
+  import("//build/config/mips.gni")

[wtc, 2015/01/07 23:56:35]

I decided to add build/config/mips.gni and declare the buildvariable
mips_arch_variant there because I found third_party/webrtc already declares that
buildvariable. It is best to declare that variable in a .gni file. Apparently
webrtc doesn't import build/config/compiler/BUILD.gn.

The companion webrtc CL is https://webrtc-codereview.appspot.com/41399004/

+}
 if (is_posix) {
   import("//build/config/gcc/gcc_version.gni")
 }
 
 import("//build/toolchain/ccache.gni")
 
 declare_args() {
   # Normally, Android builds are lightly optimized, even for debug builds, to
   # keep binary size down. Setting this flag to true disables such optimization
   android_full_debug = false
@@ skipping 245 matching lines @@
             # compiler (r5-r7). This can be verified using
             # webkit_unit_tests' WTF.Checked_int8_t test.
             "-fno-tree-sra",
 
             # The following option is disabled to improve binary
             # size and performance in gcc 4.9.
             "-fno-caller-saves",
           ]
         }
       }
+    } else if (cpu_arch == "mipsel") {
+      # Don't set the compiler flags for the WebView build. These will come
+      # from the Android build system.
+      if (!is_android_webview_build) {
+        if (mips_arch_variant == "r6") {
+          cflags += [
+            "-mips32r6",
+            "-Wa,-mips32r6",
+          ]
+          if (is_android) {
+            ldflags += [
+              "-mips32r6",
+              "-Wl,-melf32ltsmip",
+            ]
+          }
+        } else if (mips_arch_variant == "r2") {
+          cflags += [
+            "-mips32r2",
+            "-Wa,-mips32r2",
+          ]
+        } else if (mips_arch_variant == "r1") {
+          cflags += [
+            "-mips32",
+            "-Wa,-mips32",
+          ]
+        }
+      }
+    } else if (cpu_arch == "mips64el") {
+      # Don't set the compiler flags for the WebView build. These will come
+      # from the Android build system.
+      if (!is_android_webview_build) {
+        if (mips_arch_variant == "r6") {
+          cflags += [
+            "-mips64r6",
+            "-Wa,-mips64r6",
+          ]
+          ldflags += [ "-mips64r6" ]
+        } else if (mips_arch_variant == "r2") {
+          cflags += [
+            "-mips64r2",
+            "-Wa,-mips64r2",
+          ]
+          ldflags += [ "-mips64r2" ]
+        }
+      }
     }
 
     defines += [ "_FILE_OFFSET_BITS=64" ]
 
     # Omit unwind support in official builds to save space. We can use breakpad
     # for these builds.
     if (is_chrome_branded && is_official_build) {
       cflags += [
         "-fno-unwind-tables",
         "-fno-asynchronous-unwind-tables",
@@ skipping 703 matching lines @@
       cflags += [ "-gsplit-dwarf" ]
     }
   }
 }
 
 config("no_symbols") {
   if (!is_win) {
     cflags = [ "-g0" ]
   }
 }