[Android] Launch Screen 1st-step implementation

This commit is the first patch to implement LaunchScreen spec on Android.
The LaunchScreen is a static transition screen that is shown before the
user agent is able to render any HTML and CSS.
For more detailed info, please refer to below SPEC and Design Doc.

TODO:
Test will be committed in another patch
Next step implementation will support the full spec.

SPEC: https://docs.google.com/a/intel.com/document/d/17PuNuHRTQuREUpaCvj-eEx7uYi2avd-VW-oaMXMpvwo/edit?pli=1#
Design Doc: https://docs.google.com/a/intel.com/document/d/1YLajlZC7CkBOtEvzD6p6yeBr0HrPsaIGX8Eqhr3oTF4/edit#heading=h.mfsu3bk9566e
Bug: https://crosswalk-project.org/jira/browse/XWALK-637?filter=-1