Split targets mixing .c and .cc sources.

webrtc/modules/audio_device/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/webrtc.gni")
 
@@ skipping 141 matching lines @@
           ]
           defines += [ "LINUX_PULSE" ]
         }
       }
       if (is_mac) {
         sources += [
           "mac/audio_device_mac.cc",
           "mac/audio_device_mac.h",
           "mac/audio_mixer_manager_mac.cc",
           "mac/audio_mixer_manager_mac.h",
-          "mac/portaudio/pa_memorybarrier.h",
-          "mac/portaudio/pa_ringbuffer.c",
-          "mac/portaudio/pa_ringbuffer.h",
         ]
+        deps += [ ":mac_portaudio" ]
         libs = [
           # Needed for CoreGraphics:
           "ApplicationServices.framework",
 
           "AudioToolbox.framework",
           "CoreAudio.framework",
 
           # Needed for CGEventSourceKeyState in audio_device_mac.cc:
           "CoreGraphics.framework",
         ]
@@ skipping 60 matching lines @@
       "dummy/file_audio_device_factory.h",
     ]
   }
 
   if (!build_with_chromium && is_clang) {
     # Suppress warnings from the Chromium Clang plugin (bugs.webrtc.org/163).
     suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
   }
 }
 
+rtc_source_set("mac_portaudio") {
+  visibility = [ ":*" ]  # Only targets in this file can depend on this.
+  sources = [
+    "mac/portaudio/pa_memorybarrier.h",
+    "mac/portaudio/pa_ringbuffer.c",
+    "mac/portaudio/pa_ringbuffer.h",
+  ]
+}
+
 config("mock_audio_device_config") {
   if (is_win) {
     cflags = [
       # TODO(phoglund): get rid of 4373 supression when
       # http://code.google.com/p/webrtc/issues/detail?id=261 is solved.
       # legacy warning for ignoring const / volatile in signatures.
       "/wd4373",
     ]
   }
 }
@@ skipping 28 matching lines @@
       "../../system_wrappers",
       "../../test:test_main",
       "../../test:test_support",
       "../rtp_rtcp",
       "../utility",
       "//testing/gtest",
     ]
     public_configs = [ ":audio_device_config" ]
   }
 }