Add the mips_dsp_rev build variable.

build/common.gypi

 # Copyright (c) 2012 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 166 matching lines @@
         'sysroot%': '',
         'chroot_cmd%': '',
 
         # The system libdir used for this ABI.
         'system_libdir%': 'lib',
 
         # Default MIPS arch variant. This is set in the conditions block
         # below for MIPS targets.
         'mips_arch_variant%': '',
 
+        # MIPS DSP ASE revision. Possible values are:
+        #   0: unavailable
+        #   1: revision 1
+        #   2: revision 2
+        # Default: 0.
+        'mips_dsp_rev%': 0,
+
         'conditions': [
           # Ash needs Aura.
           ['use_aura==0', {
             'use_ash%': 0,
           }],
 
           # Set default value of toolkit_views based on OS.
           ['OS=="win" or chromeos==1 or use_aura==1', {
             'toolkit_views%': 1,
           }, {
@@ skipping 72 matching lines @@
         ],
       },
 
       # Copy conditionally-set variables out one scope.
       'chromeos%': '<(chromeos)',
       'chromecast%': '<(chromecast)',
       'host_arch%': '<(host_arch)',
       'target_arch%': '<(target_arch)',
       'target_subarch%': '<(target_subarch)',
       'mips_arch_variant%': '<(mips_arch_variant)',
+      'mips_dsp_rev%': '<(mips_dsp_rev)',
       'toolkit_views%': '<(toolkit_views)',
       'desktop_linux%': '<(desktop_linux)',
       'use_aura%': '<(use_aura)',
       'use_ash%': '<(use_ash)',
       'use_cras%': '<(use_cras)',
       'use_libpci%': '<(use_libpci)',
       'use_ozone%': '<(use_ozone)',
       'use_ozone_evdev%': '<(use_ozone_evdev)',
       'use_clipboard_aurax11%': '<(use_clipboard_aurax11)',
       'embedded%': '<(embedded)',
@@ skipping 766 matching lines @@
       # Set to 1 to support old history files
       'support_pre_M6_history_database%': '1',
     },
 
     # Copy conditionally-set variables out one scope.
     'branding%': '<(branding)',
     'buildtype%': '<(buildtype)',
     'target_arch%': '<(target_arch)',
     'target_subarch%': '<(target_subarch)',
     'mips_arch_variant%': '<(mips_arch_variant)',
+    'mips_dsp_rev%': '<(mips_dsp_rev)',
     'host_arch%': '<(host_arch)',
     'toolkit_views%': '<(toolkit_views)',
     'ui_compositor_image_transport%': '<(ui_compositor_image_transport)',
     'use_aura%': '<(use_aura)',
     'use_ash%': '<(use_ash)',
     'use_cras%': '<(use_cras)',
     'use_libpci%': '<(use_libpci)',
     'use_openssl%': '<(use_openssl)',
     'use_openssl_certs%': '<(use_openssl_certs)',
     'use_nss%': '<(use_nss)',
@@ skipping 1199 matching lines @@
         ],
         # Change the default to hard once the armhf transition is complete.
         'arm_float_abi%': 'softfp',
         'arm_thumb%': 1,
       }],
 
       # Set default compiler flags depending on MIPS architecture variant.
       ['target_arch=="mipsel" and mips_arch_variant=="r2" and android_webview_build==0', {
         'mips_fpu_mode%': 'fp32',
       }],
+      ['target_arch=="mipsel" and mips_arch_variant!="r6" and android_webview_build==0', {
+        'mips_float_abi%': 'hard',

[wtc, 2015/02/20 01:58:56]

The conditional expression and the default value match the code for 'mips_fpu'
in third_party/webrtc/build/common.gypi.

+      }],
 
       ['android_webview_build==1', {
         # The WebView build gets its cpu-specific flags from the Android build system.
         'arm_arch%': '',
         'arm_tune%': '',
         'arm_fpu%': '',
         'arm_float_abi%': '',
         'arm_thumb%': 0,
         'mips_fpu_mode%': '',
+        'mips_float_abi%': '',
       }],
 
       # Enable brlapi by default for chromeos.
       [ 'chromeos==1', {
         'use_brlapi%': 1,
       }],
 
       ['use_ozone==1 and ozone_auto_platforms==1', {
         # Use test as the default platform.
         'ozone_platform%': 'test',
@@ skipping 1719 matching lines @@
                     ],
                   }],
                 ],
               }],
             ],
           }],
           ['target_arch=="mipsel"', {
             'target_conditions': [
               ['_toolset=="target"', {
                 'conditions': [
                   ['android_webview_build==0 and mips_arch_variant=="r6"', {

[kjellander_chromium, 2015/02/23 13:22:35]

I suggest having a single, outer, condition block with:
android_webview_build==0
and then additional conditions blocks inside it to improve readability (and make
it possible to use else-clauses).
Applies to all the cnoditions below with android_webview_build==0 duplicated.

[wtc, 2015/02/23 20:15:51]

Done. Good suggestion.
I used an else-clause for the mips_arch_variant!="r6" block. I'm not sure if
it's more readable because now the code that sets the -m<hard|soft>-float flag
is mixed with the code that sets the mips32 revision flag.

Which form do you prefer?

                     'cflags': ['-mips32r6', '-Wa,-mips32r6'],
                     'conditions': [
                       ['OS=="android"', {
                         'ldflags': ['-mips32r6', '-Wl,-melf32ltsmip',],
                       }],
                     ],
                   }],
                   ['android_webview_build==0 and mips_arch_variant=="r2"', {
+                    'conditions': [
+                      ['mips_fpu_mode=="fp32"', {
+                        'cflags': ['-mfp32'],

[kjellander_chromium, 2015/02/23 13:22:35]

at
https://code.google.com/p/webrtc/source/browse/trunk/webrtc/build/common.gypi...
the -mips32r2 flag is added to cflags+cflags_cc for this case. 
Shouldn't they be here too, or does -mfp32 have the same effect?

[brettw, 2015/02/23 18:51:36]

cflags in GN and GYP apply to both C and C++ files. cflags_c and cflags_cc are
applied on top of those to the corresponding specific types.

So maybe the handling of -mips32r2 is wrong.

[wtc, 2015/02/23 20:15:51]

Brett, thank you for answering Henrik's question. webrtc/build/common.gypi
incorrectly adds the same compiler flag to both cflags and cflags_cc. I verified
that when compiling C++ files, that flag appears twice on the compiler command
line.

Henrik, this also answers your questions about the -mdsp and -mdspr2 below.

+                      }],
+                      ['mips_fpu_mode=="fp64"', {
+                        'cflags': ['-mfp64'],
+                      }],
+                      ['mips_fpu_mode=="fpxx"', {
+                        'cflags': ['-mfpxx'],
+                      }],
+                    ],

[wtc, 2015/02/20 01:58:56]

This block of code matches the code for 'mips_fpu_mode' in
v8/build/toolchain.gypi.

                     'cflags': ['-mips32r2', '-Wa,-mips32r2'],
                   }],
                   ['android_webview_build==0 and mips_arch_variant=="r1"', {
                     'cflags': ['-mips32', '-Wa,-mips32'],
                   }],
+                  ['android_webview_build==0 and mips_dsp_rev==1', {
+                    'cflags': ['-mdsp'],

[kjellander_chromium, 2015/02/23 13:22:35]

https://code.google.com/p/webrtc/source/browse/trunk/webrtc/build/common.gypi...
also adds this to cflags_cc. Is that redundant?

+                  }],
+                  ['android_webview_build==0 and mips_dsp_rev==2', {
+                    'cflags': ['-mdspr2'],

[kjellander_chromium, 2015/02/23 13:22:35]

https://code.google.com/p/webrtc/source/browse/trunk/webrtc/build/common.gypi...
also adds this to cflags_cc. Is that redundant?

+                  }],

[wtc, 2015/02/20 01:58:56]

This block of code matches the code for mips_dsp_rev in
third_party/webrtc/build/common.gypi.

+                  ['android_webview_build==0 and mips_arch_variant!="r6"', {
+                    'cflags': ['-m<(mips_float_abi)-float'],
+                  }],

[wtc, 2015/02/20 01:58:56]

This block of code matches the code for mips_fpu in
third_party/webrtc/build/common.gypi.

                 ],
                 'ldflags': [
                   '-Wl,--no-keep-memory'
                 ],
                 'cflags_cc': [
                   '-Wno-uninitialized',
                 ],
               }],
             ],
           }],
@@ skipping 1862 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }