H264: Thread-safe InitializeFFmpeg. Flag to control if InitializeFFmpeg should be called.

webrtc/modules/video_coding/codecs/h264/h264.gypi

 # Copyright (c) 2015 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.
 
 {
   'includes': [
     '../../../../build/common.gypi',
   ],
   'targets': [
     {
       'target_name': 'webrtc_h264',
       'type': 'static_library',
       'conditions': [
         ['OS=="ios"', {
           'dependencies': [
             'webrtc_h264_video_toolbox',
           ],
           'sources': [
             'h264_objc.mm',
           ],
         }],
         ['rtc_use_h264==1', {
           'defines': [
             'WEBRTC_THIRD_PARTY_H264',
           ],
+          'conditions': [
+            ['rtc_initialize_ffmpeg==1', {
+              'defines': [
+                'WEBRTC_INITIALIZE_FFMPEG',
+              ],
+            }],
+          ],
           'dependencies': [
             '<(DEPTH)/third_party/ffmpeg/ffmpeg.gyp:ffmpeg',
             '<(DEPTH)/third_party/openh264/openh264.gyp:openh264_encoder',
           ],
           'sources': [
             'h264_decoder_impl.cc',
             'h264_decoder_impl.h',
             'h264_encoder_impl.cc',
             'h264_encoder_impl.h',
           ],
@@ skipping 30 matching lines @@
             'h264_video_toolbox_encoder.cc',
             'h264_video_toolbox_encoder.h',
             'h264_video_toolbox_nalu.cc',
             'h264_video_toolbox_nalu.h',
           ],
         }, # webrtc_h264_video_toolbox
       ], # targets
     }], # OS=="ios"
   ], # conditions
 }