Extract use_system_foo logic out of gyp files, patch 2

third_party/libevent/libevent.gyp

 # 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.
 
 {
-  'variables': {
-    'use_system_libevent%': 0,
-  },
-  'conditions': [
-    ['use_system_libevent==0', {
-      'targets': [
-        {
-          'target_name': 'libevent',
-          'product_name': 'event',
-          'type': 'static_library',
-          'toolsets': ['host', 'target'],
-          'sources': [
-            'buffer.c',
-            'evbuffer.c',
-            'evdns.c',
-            'event.c',
-            'event_tagging.c',
-            'evrpc.c',
-            'evutil.c',
-            'http.c',
-            'log.c',
-            'poll.c',
-            'select.c',
-            'signal.c',
-            'strlcpy.c',
-          ],
-          'defines': [
-            'HAVE_CONFIG_H',
-          ],
-          'conditions': [
-            # libevent has platform-specific implementation files.  Since its
-            # native build uses autoconf, platform-specific config.h files are
-            # provided and live in platform-specific directories.
-            [ 'OS == "linux" or (OS == "android" and _toolset == "host")', {
-              'sources': [ 'epoll.c', 'epoll_sub.c' ],
-              'include_dirs': [ 'linux' ],
-              'link_settings': {
-                'libraries': [
-                  # We need rt for clock_gettime().
-                  # TODO(port) Maybe on FreeBSD as well?
-                  '-lrt',
-                ],
-              },
-            }],
-            [ 'OS == "android" and _toolset == "target"', {
-              # On android, epoll_create(), epoll_ctl(), epoll_wait() and
-              # clock_gettime() are all in libc.so, so no need to add
-              # epoll_sub.c and link librt.
-              'sources': [ 'epoll.c' ],
-              'include_dirs': [ 'android' ],
-            }],
-            [ 'OS == "mac" or OS == "ios" or os_bsd==1', {
-              'sources': [ 'kqueue.c' ],
-              'include_dirs': [ 'mac' ]
-            }],
-            [ 'OS == "solaris"', {
-              'sources': [ 'devpoll.c', 'evport.c' ],
-              'include_dirs': [ 'solaris' ]
-            }],
-          ],
-        },
+  'targets': [
+    {
+      'target_name': 'libevent',
+      'product_name': 'event',
+      'type': 'static_library',
+      'toolsets': ['host', 'target'],
+      'sources': [
+        'buffer.c',
+        'evbuffer.c',
+        'evdns.c',
+        'event.c',
+        'event_tagging.c',
+        'evrpc.c',
+        'evutil.c',
+        'http.c',
+        'log.c',
+        'poll.c',
+        'select.c',
+        'signal.c',
+        'strlcpy.c',
       ],
-    }, {  # use_system_libevent != 0
-      'targets': [
-        {
-          'target_name': 'libevent',
-          'type': 'none',
-          'toolsets': ['host', 'target'],
-          'variables': {
-            'headers_root_path': '.',
-            'header_filenames': [
-              'event.h',
+      'defines': [
+        'HAVE_CONFIG_H',
+      ],
+      'conditions': [
+        # libevent has platform-specific implementation files.  Since its
+        # native build uses autoconf, platform-specific config.h files are
+        # provided and live in platform-specific directories.
+        [ 'OS == "linux" or (OS == "android" and _toolset == "host")', {
+          'sources': [ 'epoll.c', 'epoll_sub.c' ],
+          'include_dirs': [ 'linux' ],
+          'link_settings': {
+            'libraries': [
+              # We need rt for clock_gettime().
+              # TODO(port) Maybe on FreeBSD as well?
+              '-lrt',
             ],
           },
-          'includes': [
-            '../../build/shim_headers.gypi',
-          ],
-          'link_settings': {
-            'libraries': [
-              '-levent',
-            ],
-          },
-        }
+        }],
+        [ 'OS == "android" and _toolset == "target"', {
+          # On android, epoll_create(), epoll_ctl(), epoll_wait() and
+          # clock_gettime() are all in libc.so, so no need to add
+          # epoll_sub.c and link librt.
+          'sources': [ 'epoll.c' ],
+          'include_dirs': [ 'android' ],
+        }],
+        [ 'OS == "mac" or OS == "ios" or os_bsd==1', {
+          'sources': [ 'kqueue.c' ],
+          'include_dirs': [ 'mac' ]
+        }],
+        [ 'OS == "solaris"', {
+          'sources': [ 'devpoll.c', 'evport.c' ],
+          'include_dirs': [ 'solaris' ]
+        }],
       ],
-    }],
+    },
   ],
 }