Remove crosswalk internal dependency after Crosswalk Embedding API v2

Including following changes:
1. Use crosswalk's default implementatin for
   getVideoLoadingProgressView,
   onReceivedHttpAuthRequest,
   onReceivedSslError.
2. Move onPageStarted/Finshed to CordovaChromeClient
3. Remove the customView related code in CordovaWebView as it's
   dead code.
4. Override dispatchKeyEvent instead of onKeyUp of CordovaWebView
   due to the key event handling change in crosswalk.