If duration of media source is unknown then return NaN.

content/renderer/media/android/webmediaplayer_android.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_RENDERER_MEDIA_ANDROID_WEBMEDIAPLAYER_ANDROID_H_
 #define CONTENT_RENDERER_MEDIA_ANDROID_WEBMEDIAPLAYER_ANDROID_H_
 
 #include <jni.h>
 #include <string>
 #include <vector>
@@ skipping 409 matching lines @@
   scoped_refptr<StreamTextureFactory> stream_texture_factory_;
 
   // Object for calling back the compositor thread to repaint the video when a
   // frame available. It should be initialized on the compositor thread.
   ScopedStreamTextureProxy stream_texture_proxy_;
 
   // Whether media player needs external surface.
   // Only used for the VIDEO_HOLE logic.
   bool needs_external_surface_;
 
+  // Whether valid metadata are available
+  bool has_valid_metadata_;
+
   // A pointer back to the compositor to inform it about state changes. This is
   // not NULL while the compositor is actively using this webmediaplayer.
   cc::VideoFrameProvider::Client* video_frame_provider_client_;
 
   scoped_ptr<cc_blink::WebLayerImpl> video_weblayer_;
 
 #if defined(VIDEO_HOLE)
   // A rectangle represents the geometry of video frame, when computed last
   // time.
   gfx::RectF last_computed_rect_;
@@ skipping 55 matching lines @@
 
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<WebMediaPlayerAndroid> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(WebMediaPlayerAndroid);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_ANDROID_WEBMEDIAPLAYER_ANDROID_H_