Add visibility flag to GYP.

webrtc/build/common.gypi

 # Copyright (c) 2012 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.
 
 # This file contains common settings for building WebRTC components.
 
@@ skipping 123 matching lines @@
     # Determines whether NEON code will be built.
     'build_with_neon%': 0,
 
     # Disable this to skip building source requiring GTK.
     'use_gtk%': 1,
 
     # Enable this to use HW H.264 encoder/decoder on iOS/Mac PeerConnections.
     # Enabling this may break interop with Android clients that support H264.
     'use_objc_h264%': 0,
 
+    # Enable this to prevent extern symbols from being hidden on iOS builds.
+    # The chromium settings we inherit hide symbols by default on Release
+    # builds. We want our symbols to be visible when distributing WebRTC via
+    # static libraries to avoid linker warnings.
+    'ios_override_visibility%': 0,
+
     # Determines whether QUIC code will be built.
     'use_quic%': 0,
 
     'conditions': [
       # Enable this to build OpenH264 encoder/FFmpeg decoder. This is supported
       # on all platforms except Android and iOS. Because FFmpeg can be built
       # with/without H.264 support, |ffmpeg_branding| has to separately be set
       # to a value that includes H.264, for example "Chrome". If FFmpeg is built
       # without H.264, compilation succeeds but |H264DecoderImpl| fails to
       # initialize. See also: |rtc_initialize_ffmpeg|.
@@ skipping 219 matching lines @@
         'defines': [
           'WEBRTC_POSIX',
         ],
       }],
       ['OS=="ios"', {
         'defines': [
           'WEBRTC_MAC',
           'WEBRTC_IOS',
         ],
       }],
+      ['OS=="ios" and ios_override_visibility==1', {
+        'xcode_settings': {
+          'GCC_INLINES_ARE_PRIVATE_EXTERN': 'NO',
+          'GCC_SYMBOLS_PRIVATE_EXTERN': 'NO',
+        }
+      }],
       ['OS=="ios" and use_objc_h264==1', {
         'defines': [
           'WEBRTC_OBJC_H264',
         ],
       }],
       ['OS=="linux"', {
         'defines': [
           'WEBRTC_LINUX',
         ],
       }],
@@ skipping 95 matching lines @@
           # For access to standard POSIXish features, use WEBRTC_POSIX instead
           # of a more specific macro.
           'defines': [
             'WEBRTC_POSIX',
           ],
         }],
       ],
     },
   }, # target_defaults
 }