Split TaskQueue out into a separate build target.

webrtc/base/BUILD.gn

 # Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("//build/config/crypto.gni")
 import("//build/config/ui.gni")
@@ skipping 129 matching lines @@
     "safe_conversions.h",
     "safe_conversions_impl.h",
     "scoped_ref_ptr.h",
     "stringencode.cc",
     "stringencode.h",
     "stringutils.cc",
     "stringutils.h",
     "swap_queue.h",
     "systeminfo.cc",
     "systeminfo.h",
-    "task_queue.h",
-    "task_queue_posix.h",
     "template_util.h",
     "thread_annotations.h",
     "thread_checker.h",
     "thread_checker_impl.cc",
     "thread_checker_impl.h",
     "timeutils.cc",
     "timeutils.h",
     "trace_event.h",
   ]
 
   if (build_with_chromium) {
     # Dependency on chromium's logging (in //base).
     deps += [ "//base:base" ]
     sources += [
       "../../webrtc_overrides/webrtc/base/logging.cc",
       "../../webrtc_overrides/webrtc/base/logging.h",
     ]
     include_dirs = [ "../../webrtc_overrides" ]
   } else {
     sources += [
       "logging.cc",
       "logging.h",
       "logging_mac.mm",
     ]
   }
+}
+
+static_library("rtc_task_queue") {
+  public_deps = [ ":rtc_base_approved" ]
+  configs += [ "..:common_config" ]
+
+  sources = [
+    "task_queue.h",
+    "task_queue_posix.h",
+  ]
 
   if (rtc_build_libevent) {
-    deps += [ "//base/third_party/libevent" ]
+    deps = [ "//base/third_party/libevent" ]
   }
+
   if (rtc_enable_libevent) {
     sources += [
       "task_queue_libevent.cc",
       "task_queue_posix.cc",
     ]
   } else {
-    # If not libevent, fall back to the other task queues.
     if (is_mac || is_ios) {
       sources += [
         "task_queue_gcd.cc",
         "task_queue_posix.cc",
       ]
     }
     if (is_win) {
       sources += [ "task_queue_win.cc" ]
     }
   }
@@ skipping 413 matching lines @@
     defines += [ "timezone=_timezone" ]
     sources -= [ "ifaddrs_converter.cc" ]
   }
 }
 
 source_set("gtest_prod") {
   sources = [
     "gtest_prod_util.h",
   ]
 }