webkit: HTML5 video user experience and stability fixes

- Update media player state without requiring base layer
- Show progress spinner over last video frame while buffering
- Fix VideoLayerManager tracking of textures
- Disable javascript rate change if preload not enabled
- Pass video layer ID to HTML5VideoViewProxy during creation.
  This allows the HTML5VideoViewManager in the android framework to
  determine the HTML5VideoViewProxy instance associated with the
  enterFullScreenVideo call before any video is played
- Remove videoLayerId parameter to several JNI functions
- Make animated transition user aspect-ratio-adjusted inline rectangle
- Resume video from saved position after suspend

Change-Id: Idd0853028f8ea1cbfef557263bc86b7bb1a522a5
webkit: networking optimizations

networking features:
- memory cache
- request queue priority
- event collection mechanism

Change-Id: I19b3dbe97ceddf3651f3549dfa937577149e86d7
DOM traversal optimizations DOM Core optimizations Prefetch optimization for DOM Tree Traversal

Change-Id: Ifc330c13f58c254d717d555375a584c9b7ca6479