[Android] Support shared library mode for XWalkRuntime when using WindowAndroid.

XWalkRuntime in shared mode requires WindowAndroid to have a share library context
to get resources in shared library.  Use the library context to construct WindowAndroid
in XWalkView.

BUG=https://github.com/crosswalk-project/crosswalk/issues/678 , 666
Merge pull request #724 from sqliu/otcshare-support-share-in-window

[Android] Support shared library mode for XWalkRuntime when using Window...