Add RtpHeaderExtension to avoid client breakage

webrtc/media/base/fakemediaengine.h

Index: webrtc/media/base/fakemediaengine.h
diff --git a/webrtc/media/base/fakemediaengine.h b/webrtc/media/base/fakemediaengine.h
index 1e1ef6c9db6df77bd535345f9df4136a5c620a44..b9be39bdcf8fc8b7b7d4fb0925eddcd675518ac8 100644
--- a/webrtc/media/base/fakemediaengine.h
+++ b/webrtc/media/base/fakemediaengine.h
@@ -716,6 +716,16 @@ class FakeBaseEngine {
     capabilities_.header_extensions = extensions;
   }
 
+  void set_rtp_header_extensions(
+      const std::vector<cricket::RtpHeaderExtension>& extensions) {
+    for (const cricket::RtpHeaderExtension& ext : extensions) {
+      RtpExtension webrtc_ext;
+      webrtc_ext.uri = ext.uri;
+      webrtc_ext.id = ext.id;
+      capabilities_.header_extensions.push_back(webrtc_ext);
+    }
+  }
+
  protected:
   // Flag used by optionsmessagehandler_unittest for checking whether any
   // relevant setting has been updated.
@@ -861,6 +871,15 @@ class FakeMediaEngine :
     video_.set_rtp_header_extensions(extensions);
   }
 
+  void SetAudioRtpHeaderExtensions(
+      const std::vector<cricket::RtpHeaderExtension>& extensions) {
+    voice_.set_rtp_header_extensions(extensions);
+  }
+  void SetVideoRtpHeaderExtensions(
+      const std::vector<cricket::RtpHeaderExtension>& extensions) {
+    video_.set_rtp_header_extensions(extensions);
+  }
+
   FakeVoiceMediaChannel* GetVoiceChannel(size_t index) {
     return voice_.GetChannel(index);
   }