Fixing some issues with the direction attribute of m-lines in offers.

webrtc/p2p/base/sessiondescription.h

Index: webrtc/p2p/base/sessiondescription.h
diff --git a/webrtc/p2p/base/sessiondescription.h b/webrtc/p2p/base/sessiondescription.h
index 1182a67740a725f0a3f62711dcb8c9a7f846c7ab..788016756948c1f298a17cbb87d7fb5d39cd7b3e 100644
--- a/webrtc/p2p/base/sessiondescription.h
+++ b/webrtc/p2p/base/sessiondescription.h
@@ -160,10 +160,15 @@ class SessionDescription {
   // Remove the first group with the same semantics specified by |name|.
   void RemoveGroupByName(const std::string& name);
 
+  // Global attributes.
+  void set_msid_supported(bool supported) { msid_supported_ = supported; }
+  bool msid_supported() const { return msid_supported_; }
+
  private:
   ContentInfos contents_;
   TransportInfos transport_infos_;
   ContentGroups content_groups_;
+  bool msid_supported_ = true;
 };
 
 // Indicates whether a ContentDescription was an offer or an answer, as