The screen shot support for inline video on Java side

Basically, the GL texture bound with Surface Texture is not a singleton any
more. And the Surface Texture will be recreated every time a new video starts.
This can help to recycle the decoder's memory while using the GL texture to
show the screen shot.

The corresponding webkit change is: 112500

Change-Id: I3c35f6a0abc70b9039c316ca82b236c797d81c7e