If one of the bundled content is missing in SDP, return false to MaybeEnalbeMuxingSupport().
Verified in chromium. Now the existing content still could work.

BUG=4096
TEST=Manual Test
R=juberti@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/36529004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7926 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/p2p/base/session.cc b/webrtc/p2p/base/session.cc
index 9749b14..30a9f2b 100644
--- a/webrtc/p2p/base/session.cc
+++ b/webrtc/p2p/base/session.cc
@@ -730,7 +730,12 @@
     const std::string* content_name = local_bundle_group->FirstContentName();
     const ContentInfo* content =
         local_description_->GetContentByName(*content_name);
-    ASSERT(content != NULL);
+    if (!content) {
+      LOG(LS_WARNING) << "Content \"" << *content_name

+                      << "\" referenced in BUNDLE group is not present";
+      return false;
+    }
+
     if (!SetSelectedProxy(content->name, local_bundle_group)) {
       LOG(LS_WARNING) << "Failed to set up BUNDLE";
       return false;