Remove default implementation of WebMediaPlayer::seekable()

public/platform/WebMediaPlayer.h

Index: public/platform/WebMediaPlayer.h
diff --git a/public/platform/WebMediaPlayer.h b/public/platform/WebMediaPlayer.h
index 204eb52b6b444d1da952f6672e3a639a7e707115..80cb8c59c762d04539f6c62b63e391e3d0516918 100644
--- a/public/platform/WebMediaPlayer.h
+++ b/public/platform/WebMediaPlayer.h
@@ -114,17 +114,7 @@ public:
     virtual void requestRemotePlaybackControl() { };
     virtual void setPreload(Preload) { };
     virtual WebTimeRanges buffered() const = 0;
-    virtual WebTimeRanges seekable() const
-    {
-        if (double end = maxTimeSeekable()) {
-            WebTimeRanges ranges(static_cast<size_t>(1));
-            ranges[0].start = 0.0;
-            ranges[0].end = end;
-            return ranges;
-        }
-        return WebTimeRanges();
-    }
-    virtual double maxTimeSeekable() const { return 0.0; }
+    virtual WebTimeRanges seekable() const = 0;
 
     // True if the loaded media has a playable video/audio track.
     virtual bool hasVideo() const = 0;